THE 
WONDER  OF  UFF 


By 

J.  ARTHUR  THOMSON,  M.A,  LL.D 

Regiu.-  ;  \atural   History  in  the  University    -.f  A  he*  ice- 


fSiJ  .5    .bBoT  . 


KEW     YO;*SJ 
H  !'0i,'l     AVi>     COMPANY 

*      vn^rw    MELROSE    LU; 


FiG.  1  .—The  Drama  of  Life.  (After  Roesel.)  1.  Stork  with  frog. 
2.  Tadpoles  on  weed.  3.  Salamander.  4.  Frog's  Spawn. 
5.  Toad.  6.  Lizard 


THE 
WONDER  OF  LIFE 


B7 

J.  ARTHUR  THOMSON,  M.A.,  LL.D 

Regius  Professor  of  Natural  History  in  the  University  of  Aberdeen. 

Author  of  'The  Biology  of  the  Seasons,'  'Darwinism  and 

Human  Life,'   'Heredity,'    'The   Study  of  Animal 

Life,'  'Introduction  to  Science,'  etc.,  etc 


NEW     YORK 

HENRY     HOLT    AND     COMPANY 

LONDON:  ANDREW  MELROSE  LTD 


PREFACE 

THE  aim  of  this  book  is  to  illustrate  the  ever-growing 
wonder  of  animated  Nature — with  especial  reference 
to  animal  life.  It  is  an  unconventional  introduction  to 
Natural  History  and  Biology,  taking  broad  views  of  the 
actual  lives  of  living  creatures  and  working  inwards.  It 
is  therefore  complementary  to  other  books  which  begin 
with  the  minute  analysis  of  the  individual.  The  author 
hopes  that  it  may  be  found  useful  in  '  Nature- Study ' 
as  a  continuation  of  his  Biology  of  the  Seasons,  and 
that  teachers  of  Zoology  may  recommend  it  to  their  students 
as  an  introduction  to  the  study  of  some  of  the  problems 
for  the  discussion  of  which  our  crowded  curricula  leave 
little  time. 

Recent  years  have  brought  us  a  great  increase  of  know- 
ledge in  regard  to  the  haunts  of  life,  such  as  the  Deep  Sea  ; 
periodic  movements  such  as  the  Migration  of  Birds ; 
adaptations  and  inter-relations  ;  animal  behaviour,  both 
instinctive  and  intelligent ;  the  intricacy  of  life- histories 
and  the  drama  of  organic  evolution.  It  has  been  possible, 
therefore,  in  this  book  to  use  many  fresh  facts  and  fresh 
lights  to  illustrate  and  illumine  old  problems.  The  result 
in  the  author's  mind  has  been  a  strengthening  of  the  con- 
viction that  the  facts  of  life  cannot,  for  biological  purposes, 
be  adequately  re- described  in  mechanical  formulae.  It 
is  hoped,  however,  that  dogmatism  has  been  successfully 
avoided.  The  Wonder  of  Life  must  speak  for  itself. 

Perhaps  everything  that  lives  would  appear  equally 
wonderful  if  we  knew  enough  about  it — '  the  leaf  of  grass 
no  less  than  the  journey  work  of  the  stars  .  .  .  the  pis- 
mire equally  perfect — the  egg  of  the  wren — the  tree-toad, 


2054328 


vi  PREFACE 


a  chef  tfoffuvre  for  the  highest  —  the  narrowest  hinge  in  my 
hand  —  and  the  mouse  that  is  miracle  enough  to  stagger 
sextillions  of  infidels.'  The  author  of  a  recently-published 
admirable  introduction  to  Zoology  has  used  the  motto  — 
'Ev  Traai  yap  rot?  (frvaiKOis  eveaTi  ri  Qav^a^TOv  —  and 
we  could  wish  for  no  better,  being  equally  persuaded  of  the 
cosmic  magic.  '  Prais'd  be  the  fathomless  universe,  for 
life  and  joy,  and  for  objects  and  knowledge  curious.'  It 
is  indeed  altogether  wonderful,  but  to  different  minds 
different  things  appeal  —  to  one  the  way  of  the  eagle  in 
the  air,  to  another  the  meanest  flower  that  blows.  So  we 
have  taken  a  wide  sweep  in  our  survey. 

It  is  also  true  that  science  and  age  are  ever  changing 
the  focus  of  our  wonder,  for  as  Keats  lamented,  the  rainbow 
has  never  been  quite  the  same  since  Newton  looked  at  it, 
and  the  sunbeam  that  used  to  steal  through  the  shutters 
and  dance  to  our  half  -awed  delight  many  years  ago  is 
not  quite  such  a  wonder  now.  But  new  wonders  have 
taken  the  place  of  the  sunbeams  of  our  childhood,  and  so 
it  must  always  be  for  those  who  keep  their  eyes  young, 
that  is  to  say,  scientific.  If  the  half-wonders  go,  the 
wonder  remains,  and  this  —  the  fundamental  mysterious- 
ness  of  Nature  —  is  what  we  meant  our  book  —  in  per- 
formance so  far  short  of  our  ambition  —  to  illustrate. 

My  thanks  are  due  to  Miss  Shinnie  for  her  skilful 
illustrations,  to  the  publishers  for  the  considerate  patience 
with  which  they  have  borne  delays  enforced  by  profes- 
sional duties,  and  to  Messrs.  Macmillan  for  their  kind  per- 
mission to  use  Huxley's  translation  of  Goethe's  Aphorisms. 
J.  ARTHUR  THOMSON. 

MARISCHAL  COLLEGE, 

THE  UNIVERSITY,  ABERDEEN. 
1914. 


TABLE    OF    CONTENTS 

PAGE 

PREFACE     .........          v 

INSTANCES  OF  THE  WONDER  OF  LIFE    .          .          .          .        ix 

LIST  OF  ILLUSTRATIONS         ......      xix 

CHAPTER  I 
THE  DRAMA  OF  LIFE  ;    OR,  VITAL  MOTIVES        ...         1 

CHAPTER  II 

THE  HAUNTS  OF  LIFE  ;    OR,    THE   EXPLOITATION  OF  THE 

EARTH  ........       54 

CHAPTER  III 

THE  INSURGENCE  OF  LIFE  ;    OR,   THE  CIRCUMVENTION  OF 

SPACE  AND  THE  CONQUEST  OF  TIME    .         .         .         .127 

CHAPTER  IV 

THE  WAYS  OF  LIFE  ;  OR,  MODES  OF  ANIMAL  BEHAVIOUR     .     186 
rii 


viii  CONTENTS 

CHAPTER  V  PAGE 

TH*    WEB    OF    LIFE;      OB,    THE    INTRICACY    OP    INTER- 
RELATIONS   ........     263 

CHAPTER  VI 

THE   CYCLE  OF  LIFE  ;    OR,  FROM  BIRTH  THROUGH  LOVE  TO 

DEATH 371 

CHAPTER  VII 

THE  WONDER  OF  LIFE  ;  OR,  THE  CHARACTERISTICS  OF  LIVING 

CREATURES 471 

INDEX        ........  651 


INSTANCES    OF    THE    WONDER    OF 
LIFE 

In  Illustration  of  the  Wonder  of  Life,  the  book  tells  of — 

PAGE 

millions  of  insects  on  a  glacier  ....         7 

the  bustle  of  life  on  the  heather          ....         8 

a  cataract  of  birds  and  a  great  draught  of  fishes          .         9 
the  floating  meadows  of  the  open  sea  ...       10 

the  animal  census        .          .          .          .          .          .          .11 

twenty  flowering  plants  on  a  patch  of  turf  .          .       11 

the  vultures  gathering  to  the  carcass  .          .          .          .14 

a  spider's  web    ........       14 

a  fish  that  spits  at  insects  .          .          .          .          .15 

a  spider  binding  a  grasshopper  hand  and  foot      .          .       15 
the  skua  forcing  herring  gulls  to  disgorge  their  fish        .       16 
the  land -leeches  falling  from  the  branches    .          .          .16 
a  mosquito  milking  an  ant  .....       16 

a  python's  extraordinary  meals   .          .          .          .          .17 

a  fish  swallowing  a  fish  larger  than  itself     .          .          .17 
frigate-birds  exploiting  boobies     .....       20 

birds  of  prey  thinning  bats          .....       22 

cannibal  Rotifers 23 

sea -cucumber  entangling  lobster.          ....       25 

a  fish  that  fishes 25 

butterflies  with  protective  repulsive  odours  .          .       25 

the  garment  of  invisibility  in  flat-fishes        ...       30 
the  chamseleon's  colour-change     .....       30 

the  leaf -butterfly  effacing  itself 31 

the  two  kinds  of  mimicry  .          .          .          .          32,  33 

young  mantises  like  ants     ......       34 

a  crab  masking  itself  with  a  sponge     .          .          .          .35 

a  lobster  masked  with  seaweed    .....       36 


x    INSTANCES  OF  THE  WONDER  OF  LIFE 

PAGE 

the  pistol  crab  as  a  tailor 36 

self-advertisement  among  animals 36 

the  chamaeleon's  ruse 39 

the  soap-bubbles  of  cuckoo  spit          .....  41 

experiments  in  bipedal  progression     .....  43 

a  jet  of  blood  from  the  horned  toad's  eyes         ...  47 

the  fire-fly's  courtship        .......  49 

the  male  Rhinoderma  with  eggs  hi  his  croaking-sacs  .          .  50 
paternal  care  in  hornbills            .         .          .          .          .          .51 

beetle -pets  kept  by  ants  .......  52 

the  shifts  for  a  living  on  the  sea -shore 62 

sea  slugs  secreting  dilute  oil  of  vitriol       ....  62 

a  fight  between  starfish  and  sea-urchin      .          .  63 

cannibalism  in  a  molluscan  cradle      .....  65 

paternal  care  among  shore  animals    .....  70 

the  male  stickleback's  nest         ......  70 

the  male  lumpsucker's  care  of  the  eggs      ....  70 

the  multiplication  of  palolo-worms     .....  71 

how  Ctenophores  escape  the  storms    .....  74 

open-sea  insects          ........  76 

transparent  animals  ........  78 

animal  life  in  the  great  '  deeps  '  83,    87 

a  strange,  dark,  cold,  calm,  silent,  monotonous  world          .  87 

trawling  at  a  depth  of  over  three  miles     ....  87 

the  ceaseless  rain  of  small  organisms  from  the  surface  to 

the  abysses *'..',.'•.  88 

the  absence  of  microbes  in  the  deep  sea    .         .         .          .88 

long  stalks  and  long  limbs  in  deep-sea  animals  .         .90 

abyssal  fishes  '  tumbling  upwards '  .          .          .          .91 

an  extraordinary  blind  cuttlefish  from  the  abysses      .          .  92 

bright  colours  in  a  world  of  darkness         ....  94 

iridescence  seen  on  lakes  .......  102 

three  million  Rotifers  to  the  square  yard  ....  104 

the  linkage  between  mussels  and  minnows  .  '  .  •  .  106 

the  linkage  between  bitterlings  and  mussels  .  '•  '.  '  .  106 

water-fleas  surviving  desiccation  for  nine  years  .  .  .  107 

a  leech  surviving  two  days'  imprisonment  in  ice  .  .  109 
organisms  of  the  dwarf-plankton  which  pass  through  the 

finest  pilk  gauze.  .  .  ;  .  .  .  .  110 

the  circulation  of  matter:  how  the  world  goes  round.  .  110 


INSTANCES  OF  THE  WONDER  OF  LIFE    xi 


PAGE 

the  strange  deep-water  fishes  of  Lake  Baikal      .          .          .113 
eighty  seeds  from  a  clodlet  on  a  bird's  foot       .          .          .114 
water  animals  which  do  not  get  wet  .          .          .          .115 

the  water -spider's  sub-aquatic  nest     .          .          .          .          .116 

fishes  out  of  water  .          .          .          .          .          .          .118 

the  golden  age  of  earthworms   ......     122 

caves  as  refuges  for  weaklings  ......     123 

various  solutions  of  the  problem  of  flight  ....     124 

many  different  kinds  of  '  swooping  '  Vertebrates          .          .124 
the  flights  of  gossamer  spiders  .....     126 

productivity  of  fishes,  rats,  rabbits,  etc.     ....     130 

a  starfish  with  200  million  eggs 133 

fourteen  species  on  one  stone    .          .          .          .          .          .135 

red  snow  .........     135 

spider  living  in  a  pitcher-plant  .....     137 

nets  made  by  caddis -worms 138 

the  Penelope  spider  .          .          .          .          .          .          .          .141 

the  Antarctic  fauna  .......     142 

desert  vegetation       ........     144 

rock-boring  animals  .......     145 

climbing  fishes  ........     145 

adaptations  of  aquatic  insects    ......     147 

frogs  in  salt  water    .          .          .          .          .          .          .          .148 

nesting  of  the  White  Tern 149 

remarkable  nest  of  a  tree-frog 150 

a  mouthless  carp 150 

extraordinary  tenacity  of  life 152 

life  of  tissues  and  organs  excised  from  the  body          .          .     153 
stinging  by  a  decapitated  wasp  .....     153 

the  Big  Trees,  over  2,000  years  old 154 

the  habits  of  the  land-crab 157 

skates  in  fresh  water         .......     158 

the  summer  sleep  of  mud -fishes          .          .          .          .          .160 

turning  white  in  winter     .......     162 

the  Ruffed  Grouse  beneath  the  snow          .          .          .          .162 

the  migration  of  birds       .          .          .          .          .          .          .163 

the  Arctic  Tern  in  the  Antarctic  circle       .          .          .          .165 

the  return  of  a  swallow  to  its  birth-placo  .          .          .     171 

flying  at  the  rate  of  100  miles  per  hour    ....     174 

the  power  of  way-finding  in  birds      .....     180 


xii    INSTANCES  OF  THE  WONDER  OF  LIFE 

PAOI 

the  migration  of  the  Pacific  Golden  Plover         .         .         .182 

the  behaviour  of  newly  hatched  turtles      ....  192 

movements  keeping  time  with  the  tides     ....  196 

the  behaviour  of  young  chicks 207 

lapwing's  call-note  heard  from  within  the  egg    .          .          .  209 

instinctive  behaviour  of  larval  Sphex-wasp          .          .          .  209 

sucking  instinct  of  newly-born  pig     .....  209 

effective  first  flights  of  young  swallows      .         .         .         .210 

first  webs  of  young  spiders        .         .         .         .         .         .211 

Calicurgus  wasp  disabling  a  spider     .          .          .          .          .212 

Ammophila  wasp  bruising  caterpillar's  head         .          .          .  212 
Fabre's  experiments  with  Sphex  wasp         .         .         .         .213 

foraging  and  warfare  among  Black  Termites       .          .          .  218 

unique  tactics  of  Black  Termite  soldiers     ....  222 

young  moorhen's  instinctive  diving    .....  224 

young  buzzards  excited  by  first  sight  of  adder  .         .         .  225 

wild  traits  in  tame  animals       ......  226 

remarkable  limitations  of  instinct       .....  227 

procession  caterpillars  going  in  a  circle       ....  228 

shortness  of  memory  in  caterpillars    .....  228 

instinct  of  lemmings  to  go  straight  on        ....  229 

feigning  death,  at  various  levels          .....  230 

bluffing  enemies,  as  it  seems  to  us    .         .         .         .         .231 

homing  in  ants  and  bees 233 

evidence  of  a  sense  of  direction  in  bees     ....  234 

local  memory  in  limpets    .......  235 

crabs  masking  themselves  with  seaweed      ....  236 

association  of  sensations  in  dogs  and  fishes         .          .          .  242 

association  in  hermit-crabs         ......  245 

the  trial  and  error  method 246 

behaviour  of  the  dancing  mouse 247 

plasticity  of  instinct 253 

thinking  horses  of  Elberfeld 255 

birds  essential  to  the  habitability  of  the  earth  .         .         .  266 

Nature  as  a  vast  system  of  linkages           ....  267 

connexion  between  sea -gooseberries  and  fisheries         .         .  268 

connexion  between  fishes  and  malaria         ....  269 

consequences  of  introducing  mongoose  into  Jamaica   .         .  269 

fauna  and  flora  of  birds'  feet 272 

distribution  of  seeds  by  ants 272 


INSTANCES  OF  THE  WONDER  OF  LIFE  xiii 

PAGB 

inter-relations  of  mussels  and  minnows       ....  273 

inter-relations  of  bees  and  flowers 275 

pollination  of  the  fig 280 

ambrosia 282 

inter-relations  of  a  pitcher -plant 283 

inter-relations  of  ants  and  plants        .....  285 

shelter-associations  among  animals      .....  290 

relations  between  fierasfers  and  sea-cucumbers  .          .          .  290 

partnership  between  painted  fish  and  sea-anemone      .          .  293 

commensalism  of  hermit-crabs  and  sea-anemones          .          .  294 

symbiosis  of  Algse  in  animals    ......  295 

the  double  nature  of  lichens      ......  297 

partner  microbes        ........  299 

the  adaptations  of  parasites       ......  302 

grouse-disease 303 

the  extraordinary  life-history  of  the  liver-fluke  .          .          .  307 

the  story  of  Sacculina 309 

the  story  of  ox-warbles      .......  310 

the  production  of  galls 312 

the  formation  of  pearls 313 

habits  of  the  cuckoo          .......  315 

the  gregariousness  of  fiddler-crabs 324 

division  of  labour  among  ants 326 

tailor-ants  using  larvae  as  needle  and  thread     .          .          .  328 

a  primitive  form  of  ant-society 331 

division  of  labour  among  Termites     .....  333 

reserve  '  kings  and  queens '  among  Termites       .          .          .  334 

signalling  among  Termites          ......  336 

economy  of  the  bee-hive  .......  339 

hive-bees  nesting  in  a  tree 340 

evolution  of  social  bees 341 

year's  life  of  humble-bee 343 

nest  of  a  wasp           ........  345 

animal  societies 345 

viscacha  villages        ........  350 

domestication  of  aphides  by  ants       .....  351 

guests  and  pets  of  ants     .......  352 

slave-making  among  ants            ......  354 

the  relations  of  birds  and  insects       .....  359 

house-flies  as  distributors  of  disease  .                                       .  359 


xiv  INSTANCES  OF  THE  WONDER  OF  LIFE 

PAGE 

rats,  rat-fleas,  and  plague  Bacilli 364 

yellow  fever  and  the  Stegomyia  mosquito  ....  365 

the  importance  of  the  white  heron     .....  366 

the  fate  of  the  passenger  pigeon         .....  366 

the  correlation  of  organisms  in  the  web  of  life            .          .  368 

the  various  curves  of  life           ......  373 

the  development  of  the  egg       ......  375 

development  of  a  fraction  of  an  egg           ....  378 

many  embryos  from  one  egg     ......  379 

the  ripening  of  the  egg 381 

the  fertilization  of  the  egg 382 

artificial  parthenogenesis    .......  383 

a  remarkable  case  of  hybridization    .....  389 

the  development  of  nerve-fibres          .....  390 

the  distinctiveness  of  organic  growth           ....  398 

internal  secretions  in  relation  to  growth     ....  399 

organisms  of  unlimited  growth  ......  401 

structural  registration  of  growth         .....  402 

regulation  of  growth           .......  404 

the  meaning  of  youth         .......  408 

the  play  of  animals  .         .         . '       .         .         .         .408 

courtship  among  animals   .......  410 

combats  of  males       ........  412 

significance  of  courtship-behaviour      .....  415 

habits  of  sea-lions 416 

fragrance  of  butterflies       .          .          .          .          .          .          .416 

audible  signalling  on  the  part  of  a  male  moth  .          .          .417 

post-matrimonial  cannibalism     ......  419 

parental  care 420 

paternal  care    .........  422 

the  remarkable  behaviour  of  the  bee-hunter        .          .          .  425 

habits  of  dung -rolling  beetles 426 

brooding  insects         ........  427 

over  two  thousand  feathers  from  the  nest  of  the  long-tailed  tit  427 

the  tabula  rasa  of  the  young  bird's  brain            .          .          .  430 

the  chain  of  parental  instincts            .-       .          .     .     »         .  431 

the  prevalence  of  other-regarding  activities           .          .          .  433 

longevity  of  animals            .......  435 

a  centenarian  tortoise         .......  436 

the  different  kinds  of  death                                                      .  439 


INSTANCES  OF  THE  WONDER  OF  LIFE  xv 

PAGE 

the  immortality  of  the  Protozoa         .....  440 

rarity  of  microbic  death  among  wild  animals      .          .          .  441 

the  general  occurrence  of  violent  death  in  Nature      .          .  441 

alternation  of  generations  in  hydroids         ....  444 

life-history  of  a  jelly-fish             ......  445 

remarkable  larvae  of  Echinoderms       .....  446 

story  of  horse-hair  worms            ......  447 

life -history  of  barnacles      .......  448 

life-history  of  the  shore-crab      ......  451 

life-histories  of  May-flies,  gnats,  moths        ....  452 

a  glimpse  of  a  Parthenopeia      ......  457 

the  degeneration  of  Ascidians     ......  458 

the  story  of  the  salmon  .            ......  459 

the  development  of  the  frog       ......  460 

different  forms  of  life-curve        ......  464 

the  story  of  niners    .           .......  464 

the  efficiency  of  the  living  creature  as  an  engine         .          .  473 

the  insignia  of  life     ........  474 

an  amoeba's  pursuit  of  its  prey           .....  477 

paste-eels  surviving  desiccation  for  fourteen  years        .          .  483 

seeds  germinating  after  eighty-seven  years           .          .          .  483 
white  blood  corpuscles  remaining  alive  outside  of  the  body  for 

four  and  a  half  months       ......  486 

the  puzzling  phenomena  of  luminescence    ....  487 

the  physiology  and  psychology  of  sleep      ....  494 

the  remarkable  phenomenon  of  anaphylaxis         .          .          .  501 

the  chemical  individuality  of  the  organism          .          .          .  507 

the  specificity  of  the  blood         ......  509 

the  living  creature  as  a  bundle  of  adaptations    .          .          .  510 

the  adaptations  of  the  mole 518 

Venus's  Fly-Trap  and  its  'memory'            ....  520 

snow  shoes  of  the  Ruffed  Grouse        .....  521 

an  extraordinary  egg-carrying  adaptation  in  a  male  fish       .  522 

an  egg-eating  snake,  Dasypeltis           .....  523 

Aristotle's  lantern      ........  524 

eyes  that  shine  at  night    .......  525 

adaptations  before  birth    .......  527 

the  remarkable  eyes  of  Anableps        .....  528 

warm-bloodedness  in  birds  and  mammals  ....  530 

the  ptarmigan's  heart,  adapted  to  the  mountains         .         .  532 


xvi  INSTANCES  OF  THE  WONDER  OF  LIFE 

PAGE 

the  immunity  of  hedgehog  and  some  other  mammals  to 

snake  poison        ........  532 

the  wealth  of  colouring  in  the  animal  kingdom  .         .          .  534 

the  partnership  between  Convoluta  and  an  Alga         .          .  535 

pigments  as  waste-products,  reserve-products,  and  by-products  536 

the  ripple-marks  of  growth 536 

the  internal  uses  of  pigmentation       .....  538 

the  protective  value  of  coloration       .....  539 

an  insect  protected  by  its  meals        .....  542 

the  plasticity  of  the  Msop  Prawn 545 

coloration  expressing  nervous  rhythm          ....  546 

warning  colours  among  animals           .....  548 

recognition-marks  and  guide-marks 549 

the  significance  of  the  rabbit's  white  tail  ....  549 

the  decorations  of  the  mouth  in  some  nestlings  .          .          .  549 

the  peacock's  tail                550 

a  starfish  regrown  from  a  single  arm          ....  555 

portions  of  minced  sponge  regrowing  a  whole     .          .          .  557 

regeneration  of  a  stork's  bill       ......  562 

regeneration  of  a  newt's  lens      .....       363,  570 

an  antenna  regrown  instead  of  an  eye        ....  569 

the  same  result  reached  by  different  paths          .          .          .  569 

the  regrowth  of  a  snail's  horn,  including  the  eye          .          .  571 

great  steps  in  evolution     .                 '   .          .          .          .          .  575 

the  first  making  of  a  '  body  '    .          .          .          .          .          .  576 

the  beginning  of  bilateral  symmetry            ....  576 

the  gradual  emergence  of  nobler  forms  of  life  .          .          .  577 

the  first  finding  of  a  Vertebrate  voice         ....  578 

the  steps  of  progress  made  by  Amphibians          .          .          .  578 

the  fitness  of  the  environment  to  be  a  home  of  life    .          .  579 

the  method  of  organic  evolution,  trial  and  error          .          .  582 

the  mystery  of  variations            ......  584 

the  tactics  of  Nature 586 

new  things  made  out  of  very  old  things     ....  586 

altering  the  '  time  '  of  a  vital  tune 588 

the  optimism  of  pathology 589 

trading  with  Time 591 

registration  without  memory      ......  592 

blindness  following  imprisonment  in  darkness     .          .          .  593 

a  remarkable  experiment  with  water-fleas  .,       .     ••"  .         .  597 


INSTANCES  OF  THE  WONDER  OF  LIFE  xvii 


PAGE 

development  considered  as  akin  to  recollection  .          .          .  602 

peach-trees  becoming  evergreen.          .....  602 

remarkable  experiments  with  nurse-toads   ....  604 

the  possibility  of  germinal  experiment         ....  606 

the  living  past 606 

man's  body  as  a  museum  of  relics 607 

the  vestigial  hind-limbs  of  whales 608 

the  pineal  body,  sometimes  an  eye 609 

a  two-toed  horse       .          .          .          .          .          .          .          .611 

the  stability  of  the  germ-plasm           .....  612 

a  persistent  relic  in  shrews         ......  613 

the  third  eyelid  in  man     .......  614 

the  egg-tooth  of  young  birds     ......  616 

the  hairs  of  whales  ........  618 

living  fossils,  such  as  Sphenodon        .....  620 

a  quadrupedal  young  bird,  Opisthocomus            .         .          .  620 

conservatism  in  evolution           ......  621 

the  amoeboid  growth  of  nerve-cells     .....  622 

the  distinctiveness  of  vital  activity    .....  624 

the  regulation  of  bodily  functions      .....  626 

the  complexity  of  everyday  life          .....  627 

various  examples  of  animal  behaviour,  all  requiring  historical 

explanation         ........  628 

the  migration  of  eels 630 

development  transcending  mechanical  categories           .          .  635 

the  continuity  of  evolution         ......  631 

the  achievements  of  man's  reason      .....  649 

Liesegang's  rings       ........  643 

the  fundamental  mysteriousness  of  Nature.          .          .          .  648 


LIST   OF  ILLUSTRATIONS 

(BY    ELIZABETH    L.    SHINNIE) 
FIG.  PAGE 

1.  The  Drama  of  Life.     After  Roesel   .  .        Frontispiece. 

2.  Extinct  bipedal  Reptile,  Iguanodon.     After  Dollo       .  4 

3.  Scorpion  holding  a  fly.     After  Lankester   .          .          .13 

4.  Web  of  Garden  Spider 14 

5.  Garden  Spider 15 

G.     Deep-sea  Fish,  Chiasmodon.     After  Giinther       .          .  17 

7.  Spectacled  Cobra  striking.     After  Fayrer   .          .          .19 

8.  Noctules  on  an  old  tree   .          .          .          .          .          .21 

9.  Figwort  with  pupa-cases  of  a  beetle           ...  29 
10  and  10A.       Protective    coloration  of   Flatfish.         After 

Sumner Plate  30 

11.  Leaf  Butterfly,  Kallima Plate  32 

12.  Spider  like  an  ant.     After  Peckham           ...  34 

13.  Lobster  masked  with  seaweed.     After  Williamson         .  36 

14.  Rattle  of  rattlesnake 37 

15.  Starfish  regenerating  lost  parts.     After  Mclntosh        .  39 

16.  Frilled  Lizard  running  like  a  biped.    After  Saville  Kent  43 

17.  Frilled  Lizard  at  bay.     After  Saville  Kent  ...  44 

18.  Horned  Lizard  or  Phrynosome.          .          .          .  Plate  46 

19.  Shore  scene  in  the  Mediterranean      .          .            Plate  58 

20.  Egg-capsules  of  dog-whelk 65 

21.  Free-swimming    larva    of    a    starfish,    Luidia.     After 

Mclntosh 67 

22.  Starfish,    Leptoptychaster,    with    young    ones.     After 

Challenger  Report 68 

23.  Nest  of  stickleback 69 

24.  Animals  on  sea-grass.     After  Issel     .          .          .   Plate  72 

25.  Open-Sea  Insect,  Halobates.     After  Buchanan  White  76 

26.  Jellyfish,  Dactylometra.     After  Agassiz  and  Mayer    Plate  76 

27.  Deep-sea  Crinoid,  Metacrinus                .          .          .     Plate  82 

28.  Abyssal  Pycnogonid  or  Sea-Spider.     After  Loman     .  84 

29.  Three  long-stalked  Pennatulids           ....  89 

30.  Deep-sea  Brittle  Star.     After  Koehler         ...  90 


LIST  OF   ILLUSTRATIONS 


PIG.  PAGE 

31.  Deep-sea  Cuttlefish,  Cirrothauma.     After  Chun  .     Plate   92 

32.  Two  Deep-sea  Fishes 95 

33.  Three  species  of  water-flea,  Cyclops.     After   Neubaur 

Plate  104 

34.  A  piece  of  gauze  used  in  tow-netting.     After  Lohmann  108 

35.  Organisms    of    the    Dwarf -Plankton.     After   Lohmann  110 

36.  Nets  made  by  larval  caddis-flies.     After    Wesenberg- 

Lund Plate  138 

37.  Section  through  a  land-crab.     After  Semper        .          .  157 

38.  Mudfish,  Protopterus,  in  its  summer-sleep.     After  W.  N. 

Parker 160 

39.  Young  spiders  moving  around  the  nest.     AfterHoesel     .  211 

40.  Worker  Termite.     After  Bugnion        ....  216 

41.  Worker  Termite.     After  Bugnion  and  Popoff     .          .  218 

42.  Soldier  Termite.     After  Bugnion  and  Popoff.       .         .  220 

43.  Insect  in  cataleptic  state.     After  Schmidt.          .          .  231 

44.  Bird-catching  spider  catching  a  humming-bird     Plate  242 

45.  Ctenophore  or  Sea-Gooseberry.     After  Mayer     .          .  268 

46.  Acacia  twig  tenanted  by  ants.     After  Schimper      .          .  286 

47.  Association  of  Hydractinia,  whelk,  and  hermit-crab     .  288 

48.  Fierasfers  entering  and  leaving   Holothurians.     After 

Emery Plate  290 

49.  Colonial  Radiolarian  with  partner  Algae.     After  Brandt  295 

50.  Green  Hydra  expanded  and  contracted      .          .          .  296 

51.  Stages   in    life-history  of   Liver-Fluke.     After  Thomas  308 

52.  Section  of  a  pearl.     After  Rubbell.       .           .         .  Plate  312 

53.  Shell  of  Freshwater  Mussel  with  pearls.     After  Rubbell 

Plate  314 

54.  Leaf-cutting  ants  at  work.     After  Moeller          .          .  326 

55.  Section  of  nest  of  Humble-Bee.     After  Wagner.          .  343 

56.  Nest  of  wasp.     After  Janet 345 

57.  Mosquito,  Anopheles.     After  Nuttall          .          .          .  363 

58.  Egg  of  Ascidian.     After  Duesberg      ....  375 
58 A.  Segmentation  of  the  Egg  of  a  Frog.     AfterBles      .         .  376 

59.  Chain   of  Embryos  from   one   Ovum.     After  Marchal  379 

60.  A  dividing  Cell,  showing  chromosomes.     After  Haecker  380 

61.  Diagram  of  a  Cell 387 

62.  Male  spiders  fighting.     After  Peckham       .          .          .  412 

63.  Male  spider  dancing.     After  Peckham         .          .          .  413 

64.  Female  spider  with  cocoon.     After  Blackwall     .         .  421 


LIST   OF   ILLUSTRATIONS  xxi 

FIG.  PAGE 

65.  Sea-Horscs,  Hippocampus.     After  Anthony         .          .  422 

66.  Lumpsucker,  Cyclopterus           .....  424 

67.  Emperor  Penguin  and  Young.     After  Wilson     .          .  428 

68.  Life-history  of  a  Hydrozoon.     After  Allman       .  Plate  444 

69.  Free-swimming  Larva  of  a  Sea-Cucumber           .          .  446 

70.  Free-swimming  Larva  of  a  Sea-Cucumber           .          .  446 

71.  Life-history  of  an  acorn-shell,  Balanus       .          .          .  449 

72.  Life-history  of  a  Jellyfish,  Aurelia.     After  Bronn        .  450 

73.  Larva  and  Pupa  of  a  Gnat.     After  Hurst           .          .  453 

74.  Life-history  of  Death's  Head  Moth   .          .          .  Plate  454 

75.  Metamorphosis  of  the  Eel.     After  Schmid.          .  Plate  456 

76.  Male  Edible  Frog 462 

77.  Marine  Lampreys  making  a  Nest  in  a  River        .  Plate  466 

78.  Diagram  of  a  Phosphorescent  Cell.     After  Watase.           .  488 

79.  Remarkable   Deep  Water  Fish,   Lamprotoxus.     After 

Holt  and  Byrne 493 

80.  Flounder  with  pigmented  under-side.     After  Cunningham  513 

81.  Leaf-insects.     Phyllium.              .          .          .            Plate  518 

82.  Head  of  Male  Kurtus,  carrying  eggs.    After  Weber   .  522 

83.  Mermaid's  Purse  of  Dogfish 527 

84.  Head  of  Cassowary.     After  Rothschild  and  Keulemans 

Plate  536 

85.  Two    Spiders    with    Protective    Resemblance.      After 

Vinson  and  Pickard- Cambridge  540 

88.  Umbronia,  Insect  like  a  Prickle         .          .          .          .541 

87.  Chromatophore  from  a  Prawn.     After  Degner    .          .  544 

88.  Bright  Colours  of  Littoral  Animals   .          .          .  Plate  550 

89.  Hydra  with  eight  heads.     After  Roesel  von  Rosenhof      .  552 

90.  Regeneration  of  pieces  of  Stentor.     After  Gruber        .  554 

91.  Comet  Form  of  Starfish.     After  Richters  .          .          .560 

92.  Wing  and  Wing-Bones  of  Penguin.     ^4/terPycraft           .  587 

93.  Vestigial  hip-girdle  and  hind-limb  of  Whale.     After 

Struthers 608 

94.  Pineal  Eye  of  Slow-Worm.     After  Hanitsch         .          .  609 

95.  Pineal  Eye  of  Embryo  Spheriodon.     After  Dendy       .  610 

96.  King  Crab,  Limulus 619 

97.  Peripatus.     After  Balfour 620 

98.  New  Zealand  Lizard,  Sphenodon       .          .          .          .621 

99.  Neat  of  Hornet.     After  Janet            .          .          .    Plate  628 
100.  Liesegang's  Rings.     After  Liesegang           .          .          .  643 


CHAPTER  I 

THE  DRAMA  OF  LIFE 
(VITAL  MOTIVES) 

'Sbe  performs  a  plag;  we  fcnow  notwbetber  sbe  sees  it 
berself,  ano  yet  she  acts  for  us,  tbe  lookers-on.  .  .  / 

41ber  mecbanism  baa  few  springs— but  tbeg  never  wear 
out,  are  always  active  ano  manffolo.  .  .  .' 

'Gbe  spectacle  of  IRature  is  always  new,  for  sbe  is  always 
renewing  tbe  spectators.  5Life  is  ber  most  ejquisite  inven* 
tion ;  ano  oeatb  is  ber  expert  contrivance  to  get  plenty  of 
life/ 

—Goethe's  Aphorisms,  translated  by  Huxley. 

Succession  of  Players — Progress  of  the  Drama — Primal  Impulses — 
One  Great  Problem — Abundance  of  Individuals — Number  of 
Species — Variety  of  Form — Variety  of  Bread-Winning — The 
Struggle  for  Existence — Thrust  and  Parry — Many  Inventions — 
Intricate  Situations — In  Illustration :  Cuckoo  Spit — The  Case 
of  Horned  Lizards — Love-Scenes — Family  Life — Complications 
— Retrospect. 

?  I  ^0  many  observers  of  living  creatures  it  has  seemed 
JL  as  though  they  were  being  allowed  to  see  just  a  little 
of  a  complex  and  long-drawn-out  drama.  All  the  world 
is  the  stage,  on  which,  without  any  fall  of  curtain,  scene  has 
succeeded  scene  since  life  began.  The  stage  is  crowded, 
in  spite  of  its  spaciousness,  and  everywhere  we  see  repeti- 
tions of  the  same  episodes  and  situations  on  different  scales. 
Here  there  is  a  scene  among  birds,  and  there  the  insects 


2  THE  WONDER  OF  LIFE 

show  the  same  as  if  in  miniature.  What  the  mammals 
are  acting  is  being  caricatured  by  the  amphibians  ;  and  so 
it  appears  all  round,  as  if  one  were  in  a  multiplying-mirror 
show.  It  is  like  a  world  of  echoes. 

Succession  of  Players. — The  stage  is  crowded  with 
actors  and  actresses  who  always  appear  to  be  artistic  in 
their  proper  setting  or  scenery.  Some  are  on  the  boards 
as  individuals  for  minutes,  like  some  of  the  microbes  ;  some 
for  hours,  like  some  midges  ;  some  for  days,  like  the  adult 
and  aerial  phases  of  May-flies  or  Ephemerids ;  some  for 
weeks,  like  the  house-flies ;  some  for  months,  like  the 
humble-bees ;  some  for  years,  like  the  eagle ;  some  for 
centuries,  like  the  Californian  Big  Trees ;  but  all  in  turn 
yield  to  Time's  tooth.  So  automatic,  however,  is  the  suc- 
cession among  the  short-lived  creatures  which  it  is  permitted 
to  any  one  of  us  to  observe,  that  no  gap  is  ever  apparent. 
There  is  always  an  understudy  ready  to  fill  the  vacant  place. 
When  we  lengthen  out  our  vision  scientifically  we  see, 
however,  that  in  spite  of  the  apparent  sameness  there  is 
continual  change,  and  that  one  cast  succeeds  another 
as  age  follows  age.  Many  great  actors  of  superlative 
merit,  like  the  Sea-Scorpions,  the  Giant  Saurians  and 
the  Flying  Dragons,  have  altogether  ceased  to  be,  and 
have  left  no  direct  successors  at  all.  Nor  has  their 
mantle  fallen  on  any.  The  play  goes  on,  but  the  players 
change. 

Progress  of  the  Drama. — The  age-long  drama,  whose 
progress,  or,  it  may  be,  merely  changeful  sequence,  is  called 
Evolution,  was  aptly  likened  by  Samuel  Butler  to  the 
development  of  a  fugue,  '  where,  when  the  subject  and 
counter-subject  have  been  announced,  there  must  thence- 
forth be  nothing  new,  and  yet  all  must  be  new.  So  through- 


THE   DRAMA   OF  LIFE  3 

out  organic  nature — which  is  a  fugue  developed  to  great 
length  from  a  very  simple  subject — everything  is  linked  on 
to  and  grows  out  of  that  which  comes  next  to  it  in  order — 
errors  and  omissions  excepted '.  '  And  yet  all  must  be 
new  ',  for  it  would  not  be  a  drama  if  it  did  not  develop,  and 
it  would  not  be  life  if  it  were  not  creative.  The  Aristotelian 
maxim  that  there  is  nothing  in  the  end  which  was  not  also  in 
the  beginning,  is  true  if  we  believe  that  in  the  beginning  was 
the  Logos.  Otherwise  it  requires  safeguarding.  For  while 
individual  development  is  the  expression  or  realization  of 
the  given  inheritance,  it  is  a  self-expression  that  can  only 
come  about  by  trafficking  with  the  environment,  and  may 
greatly  enrich  itself  in  so  doing.  And  similarly,  through 
the  ages,  the  evolving  organisms  have  been  trading  with 
Time,  and  thus  '  all  must  be  new '. 

Beyond  doubt  the  most  impressive  fact  about  animate 
nature  is  the  ascent  of  life.  It  has  gone  on,  reaching  from 
step  to  step  in  a  manner  for  which  we  have  no  word  but 
progress.  Its  historic  movement,  as  Lotze  finely  said,  is  like 
that  of  an  onward-advancing  melody.  It  is  a  fact  that 
nobler  and  finer  forms  of  life  have  appeared  on  the  world's 
stage  as  one  geological  period  has  succeeded  another. 
The  bodies  of  animals  have  become  more  complex  and 
more  controlled,  that  is  to  say  in  technical  terms,  more 
differentiated  and  more  integrated.  The  life  of  the  creature 
has  escaped  more  and  more  from  the  thraldom  of  the 
environment.  We  instinctively  think  of  a  bird  as  the 
emblem  of  freedom.  There  has  been  an  increasing  ampli- 
tude in  life,  as  is  evident  when  we  compare  birds  and 
mammals  with  amphibians  and  fishes,  or  insects  and 
spiders  with  sea-urchins  and  medusae.  There  has  been,  it 
appears  to  us,  an  increasing  liberation  of  the  Psyche  ; 


4  THE  WONDER  OF  LIFE 

there  is  more  and  more  behaviour  as  we  ascend,  and  we 
may  even  discern  the  springs  of  conduct. 

It  must  not  be  supposed,  however,  that  the  history 
discloses  any  straightforward  progress,  for  it  is  full  of 
retrogressions  and  of  strange  culs-de-sac.  The  tapeworm 


FIG.  2. — Extinct  bipedal  Reptile,  Iguanodon  mantelli,  about  12  feet 
high.  The  genus  is  restricted  to  the  Wealden  (Cretaceous).  (After 
Dollo.) 


is  as  much  a  product  of  evolution  as  the  bird,  and  is  as 
well  adapted  to  its  inglorious  lot  as  the  lark  to  heaven's 
gate.  There  have  been  extraordinary  failures,  too,  in  the 
sense  that  many  extinct  types  of  great  perfection  have 
left  no  direct  descendants.  We  do  not  know  that  their 


THE  DRAMA  OF  LIFE  5 

particular  excellences  have  in  any  way  passed  into  those 
who  continue  the  march,  except  in  the  very  indirect  sense, 
perhaps,  that  Man,  for  instance,  is  the  stronger  because  of 
his  early  antagonists  like  the  Cave  Lion  and  the  Cave  Bear, 
who  have  long  since  ceased  to  be. 

In  the  history  of  life  we  may  recognize,  with  Bergson, 
three  main  lines  of  evolution.  (I)  There  is  the  vegetative 
line,  followed  by  plants,  and  in  great  measure  by  such 
animals  as  hydroids  and  corals.  (II)  There  is  the  in- 
stinctive line,  followed  especially  by  the  chitin-clad  small- 
brained  Arthropods  (Crustaceans,  Insects,  Spiders,  and  the 
like).  (Ill)  There  is  the  intelligent  line,  followed  more 
especially  by  the  Vertebrates,  where  an  internal  skeleton 
of  bone  usually  takes  the  place  of  the  Arthropod's  external 
skeleton  of  chitin,  and  where  the  cerebral  part  of  the 
nervous  system  attains  high  development.  A  Calif ornian 
Big  Tree,  two  thousand  years  old,  may  represent  the 
climax  of  I ;  an  ant  the  climax  of  II ;  and  a  man  the 
climax  of  III. 

Primal  Impulses. — What  in  this  world-fugue  is  the 
subject  and  what  the  counter-subject  ?  There  can  be 
little  doubt  that  the  answer  must  be — Hunger  and  Love. 
These  are  the  two  primal  impulses. 

Warum  strebt  sich  das  Volk  so,  und  schreiet  ? 
Es  will  sich  nahren,  Kinder  zeugen,  und  sie  ernahren  so  gut 
es  vermag. 

These  words  '  hunger  '  and  '  love  '  must  not  indeed  be 
used  woodenly  ;  they  correspond  to  self-preservation  and 
race-continuance,  to  self-regarding  and  other-regarding, 
to  nutrition  and  reproduction,  to  self-increase  and  self- 
multiplication,  to  feeding  and  flowering,  and  so  on.  It  is 


6  THE  WONDER  OF  LIFE 

well  understood  that  while  Charles  Darwin's  grandfather 
wrote  a  book  about  The  Loves  of  the  Plants,  it  is  not 
particularly  useful  for  us  to  employ  such  a  phrase.  Never- 
theless, it  is  entirely  sound  science  to  emphasize  the 
fact  that  rich  as  plants  are  in  adaptations  which  secure 
food,  they  are  not  less  rich  in  adaptations  which  secure 
the  nurture  and  dispersal  and  development  of  their  off- 
spring. 

One  is  tempted  sometimes  to  say  that  the  primal  impulse 
of  organisms — even  before  hunger  and  love — is  self- 
assertion,  self-expression,  and  insurgence.  But  these  big 
words  are  all  covered  by  the  little  word  '  life '.  For  life 
is  activity,  effective  activity,  regulated  activity,  self-asser- 
tive activity.  If  we  start  with  this  postulate,  we  may 
then  say  that  the  mainsprings  of  an  organism's  activity 
may  be  summed  up  in  the  words — '  hunger  '  and  '  love  ', 
the  imperious  motive  forces  of  life. 

One  Great  Problem. — As  we  contemplate  the  drama, 
both  as  we  can  see  it  with  our  eyes,  and  as  we  can  see  it 
with  the  help  of  telephotic  apparatus  (such  as  a  palaeonto- 
logical  museum  !),  we  may  discern  that,  in  spite  of  all  the 
variety,  there  is  one  perennial  problem  and  endeavour, 
namely,  to  adjust  relations  between  the  active,  self-asser- 
tive, insistent,  insurgent  organism  and  the  inert,  indifferent, 
heavy-handed  environment.  Living  has  often  been  de- 
scribed as  action  and  reaction  between  the  organism  and 
the  environment,  but  this  is  not  quite  adequate.  The  facts 
of  the  case  have  been  better  stated  by  Prof.  Patrick  Geddes. 
On  the  one  hand,  the  Enviroment  acts  upon  the  organism, 
burning  it  and  stoking  it,  heating  it  and  cooling  it,  quicken- 
ing it  and  slowing  it,  moistening  it  and  drying  it,  exciting 
it  and  quieting  it,  and  so  on.  The  organism  being  acted 


THE  DRAMA  OF  LIFE  7 

upon,  the  relation  may  be  formulated  as  E-*>f  -*•  o  (the  first 
letters  of  the  words  Environment,  function,  and  organism). 
On  the  other  hand,  the  Organism  (to  which  we  may  now 
give  the  capital  letter)  not  only  reacts,  it  acts.  It  hits 
back  ;  it  thrusts  ;  it  operates  upon  its  environment.  The 
environment  being  acted  upon,  the  relation  may  be  formu- 
lated as  0->f->e.  The  real  business  of  life  is  an  adjustment 

0^-f^e 

of  the  twofold  relation  :  =—f — ;  and  that  is  what  we  see 
E^f-»o 

continually  going  on  in  the  drama  of  life. 

Abundance  of  Individuals. — We  have  spoken  of  the 
crowded  stage,  and  the  prodigality  of  life  is  certainly 
one  of  its  characteristics.  Antarctic  explorers  have  told 
us  that  in  one  haul  of  the  dredge  in  those  icy  waters 
it  was  quite  a  usual  thing  to  get  from  ten  thousand 
to  thirty  thousand  specimens  of  a  certain  Crustacean. 
On  the  surface  of  the  small  pools  of  water  on  the 
melting  ice  of  the  mer  de  glace  at  Chamonix,  M.  Vallot 
found  in  1912  an  extraordinary  multitude  of  a  rather 
rare  wingless  insect,  the  '  glacier  flea  ',  Desoria  nivalis. 
These  minute  and  primitive  forms  occurred  over  a 
stretch  of  glacier  twenty  metres  broad  by  two  thousand 
metres  long,  and  there  must  have  been  forty  millions  of 
them  ! 

The  heather  on  the  moor,  with  its  firm  leaves  and  appar- 
ently clean  twigs,  does  not  suggest  itself  as  a  crowded  home 
of  life,  but  that  is  just  what  it  is,  as  Dr.  Shipley  found  in 
searching  for  grouse-parasites.  He  adopted  the  method 
of  soaking  the  heather  in  water  and  then  centrifuging  the 
infusion,  with  the  result  that  an  extraordinary  wealth  of 
little  creatures  was  discovered.  He  gives  a  striking  picture 
of  what  would  appear  if  we  could  see  a  square  yard  of 


8  THE  WONDER  OF  LIFE 

the  moor  through  a  gigantic  lens,  magnifying  a  hundred 
times  : — 

'  The  heather  plants  would  be  as  tall  as  lofty  elms,  their 
flowers  as  big  as  cabbages,  the  grouse  would  be  six  or  seven 
times  the  size  of  '  Chantecler '  at  the  Porte  St.  Martin  ; 
creeping  and  wriggling  up  the  stem  and  over  the  leaves, 
and  gradually  yet  surely  making  their  way  towards  the 
flowers,  would  be  seen  hundreds  and  thousands  of  silvery 
white  worms  about  the  size  of  young  earthworms.  Lying 
on  the  leaves  and  on  the  plant  generally  would  be  seen 
thousands  of  spherical  bodies  the  size  of  grains  of  wheat,  the 
cysts  of  coccidium  [a  minutely  microscopic  Protozoon 
parasite] ;  and  on  the  ground  and  on  the  plants,  as  large  as 
split  peas,  would  be  seen  the  tapeworm  eggs  patiently 
awaiting  the  advent  of  their  second  host.  It  is  perhaps  a 
picture  that  will  not  appeal  to  all,  yet  it  represents  what, 
unseen  and  unsuspected,  is  always  going  on  upon  a  grouse 
moor.'  [The  Grouse  in  Health  and  Disease,  1911.] 

It  may  be  said  that  the  naturalist  has  beyond  all  others 
a  discipline  in  the  fine  art  that  Blake  spoke  of  as  grasping 
infinity  in  the  palm  of  the  hand.  Even  about  the  dry 
twigs  of  the  heather,  there  is  a  bustle  of  life. 

Sometimes  we  get  an  impression  of  the  prodigal  wealth 
of  life  with  overwhelming  convincingness.  Describing  a 
visit  to  a  Lapland  bird-berg,  the  nesting- place  of  guillemots, 
razor-bills,  and  puffins,  the  naturalist  Brehm  wrote  : — 

*  The  whole  hill  was  alive.  Hundreds  of  thousands  of 
eyes  looked  upon  us  as  we  intruded.  From  every  hole  and 
corner,  from  every  peak  and  ledge,  out  of  every  cleft, 
burrow,  or  opening,  they  hurried  forth,  right,  left,  above, 
beneath;  the  air,  like  the  ground,  teemed  with  birds. 
From  the  sides  and  from  the  summit  of  the  berg  thousands 


THE    DRAMA   OF  LIFE  9 

threw  themselves  like  a  continuous  cataract  into  the  sea 
in  a  throng  so  dense  that  they  seemed  to  the  eye  to  form 
an  almost  solid  mass.  Thousands  came,  thousands  went, 
hundreds  of  thousands  swam  and  dived,  and  yet  other 
hundreds  of  thousands  awaited  the  footsteps  which  should 
rouse  them  also.  There  was  such  a  swarming,  whirring, 
rustling,  fluttering,  flying,  and  creeping  all  about  us  that  we 
almost  lost  our  senses.  .  .  .  The  cloud  of  birds  around  us 
at  the  summit  was  so  thick  that  we  only  saw  the  sea  dimly 
and  indefinitely  as  in  twilight.  .  .  .  The  millions  of  which 
I  had  been  told  were  really  there.' 

Speaking  of  the  dense  swarms  of  haddocks  and  the  like 
which  throng  at  the  spawning  time  into  the  Norwegian 
fjords,  the  same  naturalist  says  : — 

'  Animated,  almost  maddened,  by  one  impulse,  the  fish 
swim  so  thickly  that  the  boat  has  literally  to  force  a  way 
among  them,  that  the  overweighted  net  baffles  the  com- 
bined strength  of  the  fishermen  or  breaks  under  its  catch, 
that  an  oar  placed  upright  among  the  densely  packed  crowd 
of  swimmers  remains  for  a  few  moments  in  its  position  be- 
fore falling  to  one  side.' 

Perhaps  this  final  touch  is  exaggerated,  but  the  general 
impression  has  been  verified  many  times  in  the  lochs  in  the 
West  of  Scotland. 

The  prodigal  abundance  of  larger  forms  of  life  implies 
the  still  greater  abundance  of  small  fry,  for  all  are  linked 
by  nutritive  chains.  It  is  in  the  open-water  of  lake  and 
sea  that  we  get  our  best  impressions  of  multitudinousness. 
At  the  spring  maximum  of  the  Rotifer  or  Wheel- Animalcule 
called  Synchceta,  there  may  be  about  three  millions  to  a 
square  yard  of  lake  ;  at  the  summer  maximum  of  the  slimy 


io  THE  WONDER  OF  LIFE 

Alga,  Clathrocystis  ceruginosa,  there  may  be  500  millions 
to  the  square  yard ;  at  the  autumn  maximum  of  a  well- 
known  Diatom  Melosira  varians,  which  has  a  summer 
maximum  as  well,  there  are  about  7,000  millions  to  the 
square  yard,  so  that  the  waters  of  the  lake  form  a  veritable 
living  soup.  Perhaps,  outside  of  Bacteria,  this  is  near  the 
climax  of  productivity. 

The  same  exuberant  productivity  is  equally  characteristic 
of  many  tracts  of  the  open  sea,  where  a  vessel  may  steam 
for  days  through  floating  meadows,  several  feet  deep,  of 
simple  vegetation — mostly  consisting  of  unicellular  Algae. 
Thus  clusters  of  threads,  called  Trichodesmium,  may  collect 
on  the  surface  in  calm  weather,  like  unmelting  yellowish- 
brown  snowflakes,  and  extend  over  many  acres.  In  an 
ordinary  sample  from  a  warm  part  of  the  Atlantic  and 
from  a  depth  of  50  metres  (which  is  the  most  densely 
peopled  zone  as  far  as  plants  go),  there  are  likely  to  be 
about  5,000  plant-cells  in  a  litre ;  but  there  may  be  as 
many  as  a  quarter  of  a  million,  which  is  a  prodigious 
exuberance  of  life. 

Number  of  Species. — There  might  be  great  abundance 
of  life  and  yet  no  conspicuous  variety,  but  every  one 
knows  that  the  number  of  different  kinds  of  animals  and 
plants  is  far  beyond  what  we  can  readily  conceive.  Aris- 
totle recorded  about  500  animals,  but  a  single  expedition 
nowadays  may  still  discover  more  than  a  thousand  new 
species — most  of  them  rather  small  deer  we  must  admit. 
We  are  amazed  at  the  number  of  stars  which  we  can  see 
definitely  on  a  clear  night,  perhaps  four  thousand  alto- 
gether, but  there  may  be  more  species  in  one  family  of 
insects. 

In  the  small  island  of  Britain  there  is  a  record  of  the 


THE  DRAMA  OF  LIFE  n 

occurrence  of  about  462  different  kinds  of  birds,  and  the 
total  number  of  living  species  of  birds  may  be  safely 
estimated  at  not  less  than  ten  thousand. 

Dr.  Gadow,  writing  in  1898,  estimated  the  number  of 
recent  species  of  Vertebrate  animals  at  24,241.  He  put 
Mammals  at  2,702,  Birds  at  9,818,  Reptiles  at  3,441,  Amphi- 
bians at  925,  Fishes  at  7,328,  and  primitive  Vertebrates 
at  27.  But  it  is  when  we  pass  to  the  Invertebrates  that 
the  numbers  of  species  mount  up  so  enormously.  Thus  an 
authority  on  Diptera  has  put  the  probable  number  of 
species  at  a  hundred  thousand,  and  there  is  no  doubt  that 
there  are  many  times  more  species  of  insects  than  of  all 
other  animals  put  together.  Dr.  Sharp  remarks  that 
though  the  largest  insects  scarcely  exceed  in  bulk  a  mouse 
or  a  wren, '  yet  the  larger  part  of  the  animal  matter  existing 
on  the  lands  of  the  globe  is  in  all  probability  locked  up  in 
the  forms  of  Insects  '. 

The  same  authority  estimates  the  number  of  named 
species  of  insects  at  250,000  ;  and  suggests  that  this  is  only 
about  a  tenth  of  the  total.  It  has  been  estimated  that 
there  are  about  200,000  plants,  of  which  about  a  half  are 
Dicotyledonous  Flowering  Plants.  But  even  more  im- 
pressive is  Darwin's  record  of  finding  twenty  species  of 
Flowering  Plants  in  a  patch  of  turf  four  feet  by  three ; 
or  the  finding  of  four  hundred  in  a  square  mile. 

Variety  of  Form. — There  are  not  very  many  main  styles 
of  architecture  among  animals,  but  there  is  endless  variety 
in  detail.  All  the  Vertebrates  are  obviously  reducible  to 
one  style  of  architecture,  but  what  contrasts  there  are  be- 
tween eagle  and  whale,  between  tortoise  and  snake,  between 
eel  and  skate,  between  frog  and  newt,  between  swift  and 
penguin,  between  weasel  and  giraffe,  between  minnow  and 


12  THE  WONDER  OF  LIFE 

man,  and  so  one  might  continue  for  a  long  time.  Among 
Invertebrates,  the  unicellulars  or  Protozoa  form  a  sub- 
kingdom  by  themselves  ;  the  Sponges  and  Stinging  Animals 
ring  the  changes  on  the  possibilities  of  radial  symmetry ; 
Worms  present  a  bewildering  variety  of  types  with  little  in 
common  save  the  general  tendency  to  be  '  worm-like ' ; 
Echinoderms,  though  a  very  well- defined  series,  show  aston- 
ishing contrasts, — between  brittle-star  and  sea-urchin, 
between  the  sausage-like  sea-cucumber  and  the  graceful  sea- 
lily.  The  two  other  great  series  are  the  Arthropods  and  the 
Molluscs,  sharply  contrasted  at  almost  every  point.  Among 
Molluscs  we  may  compare  oyster  with  cuttlefish,  slug  with 
nautilus,  land-snail  with  '  sea-butterfly  ' ;  it  is  difficult 
for  the  ordinary  observer  to  understand  on  what  grounds 
such  dissimilar  forms  can  be  united  under  one  title.  Simi- 
larly, the  exceedingly  successful  Arthropod  series,  rivalled 
only  by  the  Vertebrates,  includes  Crustaceans,  Centipedes, 
Insects,  Spiders,  Scorpions,  Mites  and  many  other  very 
divergent  types.  If  we  consider  Crustaceans,  we  get  the 
same  impression, — water-fleas  and  lobsters,  fish- lice  and 
land-crabs,  sand- hoppers  and  barnacles — what  a  variety  of 
form !  The  crowning  illustration  is  surely  among  Insects, 
where  within  a  relatively  narrow  range  we  find  an  astonish- 
ing wealth  of  style, — the  squat  bug  and  the  lank  walking- 
stick  insect,  the  heavy  beetle  and  the  dainty  midge,  the 
butterfly  and  the  flea,  the  mosquito  and  the  cockroach.  It 
has  also  to  be  remembered  that  there  are  many  less  familiar 
types  of  animal  life  which  represent  quite  distinct  lines  of 
their  own,  such  as  Rotifers,  Polyzoa,  and  Brachiopods, 
which  greatly  increase  the  range  of  diversity  of  forms. 

Variety  of  Bread -Winning. — In  illustration  of  variety 
of  habit,  let  us  recall  for  a  moment  the  variety  of  food- 


THE  DRAMA  OF  LIFE  13 

getting  among  birds — the  blackbird  gobbling  the  belated 
worm  in  the  early  morning,  the  thrush  making  a  '  kitchen- 
midden  '  of  snail  shells,  the  humming-bird  sipping  nectar 
from  the  flowers,  the  oyster-catcher  jerking  the  limpets 
off  the  sea-shore  rocks,  the  woodcock  probing  for  earth- 


FIG.  3. — A  Scorpion,  Euscorpius,  holding  a  fly  in  one  of  its  claws,  or 
pedipalps,  and  piercing  it  with  its  sting.     (After  Lankester.) 

worms  among  the  mould,  the  stately  heron  fishing  by  the 
side  of  the  stream,  the  eagle  in  low  flight  searching  the 
mountain-side  for  grouse,  the  secretary-bird  striking  the 
snakes  in  the  South  African  karoo,  the  cross-bill  deftly 
tearing  up  the  cones  on  the  fir  trees. 

It  seems  certain  that  vultures  and  the  like  discover  their 
prey  by  sight  and  not  by  smell.  Sometimes  they  seem  to 
keep  definite  '  preserves  '  in  the  sky,  and  when  one  sees  the 
carcass  and  descends  upon  it,  his  neighbour  in  the  next 
'  preserve '  follows  suit,  and  another  and  another  as  the 
news  passes  through  the  heavens.  A  fine  picture  of  this  is 
given  in  Hiawatha — 

'  Never  stoops  the  soaring  vulture 
On  his  quarry  in  the  desert 
On  the  sick  or  wounded  bison, 


THE  WONDER   OF   LIFE 


But  another  vul- 
ture, watching 

From  his  high 
aerial  look-out, 

Sees  the  down- 
ward plunge 
and  follows, 

And  a  third  pur- 
sues the  second, 

Coming  from  the 
invisible  ether, 

First  a  speck  and 
then  a  vulture 

Till  the  air  is  dark 
with  pinions '. 

And  then 
it,  comes  the 

blinding  poetic 
R  flash- 

'So  disasters 
come  not 


55 


FL 


singly  '. 

There  are 
humdrum  ways 
of  getting  food, 
which  the 
grazing  herds 
illustrate.  But 

FIG.    4.—  Web  of  Garden   Spider.     The  spinner     how    often  this 
makes  first  the  strong  foundation-lines    (FL). 
Then  the  rays  (B)  are  made.     Third,  a  non- 
viscid   primary   spiral    (PS)   is  formed,  as  a 
scaffolding,      from     the      centre     outwards.  .       ,  ,      . 

Fourthly,  this  is  replaced  by  the  viscid  dramatically! 
secondary  spiral  (ss),  which  is  the  genuine  JjJverV  one  has 
web,  made  from  the  outside  inwards.  ' 

heard     of    the 

Archer  or  Spitting  Fish  (Toxotes)  of  Malay,  which  shoots 


• 
s  e  l 

is    solved 


THE  DRAMA   OF  LIFE 


from  its  mouth  a  long  jet  of  water  and  with  accurate  aim 
secures  a  coveted  insect  which  was  sunning  itself  on  the 
plants  overhanging  the  stream.  The  larva  of  the  ant-lion 
digs  a  funnel-like  pit  in  the  sand  and  lurks  at  the  foot  to 
seize  small  insects  that  roll  down  ;  and  the  larval  Cicindela 
makes  a  vertical  tube,  '  in  which  he  props  himself  like 
a  chimney  sweep  climbing  up  a  chimney  ',  so  that  his 
head  forms  a  lid  on  the  level  of  the  ground.  M.  Henri 
Coupin  describes  the  procedure  : 
'  When  a  little  creature  is  about 
to  pass  over  this  veritable  living 
trap  the  larva  sinks  down,  at 
the  same  time  dragging  with 
him  his  victim,  which  he  hastens 
to  seize  between  his  claws  and 
to  devour '.  Spiders'  webs  and 
snares  illustrate  another  method 
which  has  often  its  detailed 
subtleties.  Thus  M.  Coupin 
refers  to  Vinson's  discovery  of 
the  use  of  a  strong  silken  string 
bent  in  zigzag  in  the  middle  of  the 

web  of  a  Madagascar  spider,  which  makes  a  construction 
very  much  like  that  of  the  common  Epeira  diadema  of  our 
gardens.  The  cable  must  be  of  use,  for  if  it  be  removed  it 
is  at  once  replaced  by  another,  but  what  can  its  use  be  ? 
The  answer  was  forthcoming  one  day  when  Vinson  saw  a 
large  grasshopper  jump  into  the  web,  and  saw  the  spider 
hastily  seize  the  cable  and  wind  it  round  the  unusual 
victim,  who  was  too  big  to  be  held  by  the  usual  fine  threads  ! 
There  is  such  an  embarrassing  number  of  strange  ways  of 
getting  food  that  it  is  difficult  to  pick  and  choose, — some 


FIG.  5. — Garden  Spider, 
Epeira  diadema,  female. 


16  THE  WONDER  OF  LIFE 

lurk  like  the  crocodiles,  some  act  burglar  like  the  ant-eater 
bursting  into  the  termitary,  some  hunt  in  packs  and  some 
alone,  some  utilize  what  others  have  won.  Thus  in  the 
North  of  Scotland  it  is  not  an  uncommon  sight  to  see  a 
Skua  gull  (Stercorarius)  chivying  herring  gulls  in  the  air 
until  they  disgorge  their  last  caught  fish.  It  is  an  astonish- 
ing fact  that  this  should  be  sometimes  re-caught  by  the 
skua  before  it  reaches  the  water.  What  a  long  gamut 
there  is  between  the  behaviour  of  these  skuas  and  the  land 
leeches  in  the  tropical  forest !  '  Only  too  frequently  ',  says 
M.  Coupin,  '  one  hears  a  sudden  noise  like  hail  falling  on  the 
branches.  It  is  not  falling  hail,  but  leeches,  which  hasten 
to  attach  themselves  to  beasts  of  burden  and  to  men,  from 
whom  they  proceed  to  suck  the  blood.  They  were  watching 
[sic]  their  chance,  perched  on  the  branches — an  odd 
dwelling-place,  by  the  way,  for  creatures  that  are  generally 
considered  aquatic '. 

We  have  referred  in  "  The  Biology  of  the  Seasons  "  to 
Jacobson's  extraordinary  story  of  a  mosquito  milking  an 
ant.  For  that  is  what  it  comes  to.  The  mosquito  frequents 
certain  trees  in  Java  on  which  the  ants  (Cremastogaster 
diformis)  go  to  and  fro.  It  hails  a  passing  ant  and  strokes 
her  head  with  quick  movements  of  fore-legs  and  antenna. 
Perhaps  it  tickles,  perhaps  it  massages  the  ant — who  can 
tell  ?  It  seems  to  please  her  anyhow,  for  she  emits  a  drop 
of  juice  which  the  mosquito  sucks  up.  The  mosquito 
has  been  named  Harpagomyia  splendens  by  de  Meijere, 
who  points  out  that  the  creature  cannot  bite.  But  to 
beg  it  is  not  ashamed.  Jacobson  found  two  other 
Dipterous  insects  in  Java  which  seem  also  to  have  learned 
how  to  tap  ants.  These  extraordinary  inter-relations 
recall  the  well-known  but  very  remarkable  fact  that 


THE  DRAMA  OF  LIFE  17 

several  species  of  ants  keep  Aphides  or  green  flies  as  their 
cows  (vacccB  formicantm  as  Linnaeus  said),  utilizing  the 
sweet  fluid  which  they  exude  when  they  are  stroked. 
The  ants  take  some  care  of  the  Aphides  and  resent  inter- 
ference with  their  property. 

Milking  ant  or  aphis  is  dainty  feeding  ;  contrast  it  with  a 
python's  meals.  A  specimen  of  Python  reticulata,  about 
25  feet  long,  which  was  observed  in  Hagenbeck's  zoological 
garden,  swallowed  a  swan  of  18  Ib.  and  two  days  later  a 
roebuck  of  67  Ib.  Another  swallowed  within  two  days 
two  roebuck  of  28  Ib.  and  39  Ib.,  and  soon  thereafter  a 
chamois  of  71  Ib.  In  another  case  a  goat  of  84  Ib.  in 
weight  was  engulfed,  and  took  about  nine  days  to  digest. 
The  pharynx  can  be  dilated  to  a  width  of  over  a  yard. 
After  a  meal  the  pythons  remain  inert,  and  it  should  be 
>noted  that  although  they  often  eat  much,  they  do  not  need 
to  eat  often  !  Two  of  them  remained  in  good  condition 
from  spring  to  November  without  eating  at  all. 

The  voracity  of  some  of  the  Deep- Sea  Fishes  goes  beyond 


FIG     6. — A  Deep-Sea  Fish  (Chiasmodon  r.iger),  whose  distended  stomach 
contains  a  larger  fish.     (After  Giinther.) 

C 


i8  THE  WONDER  OF  LIFE 

bounds.  Thus  it  is  recorded  that  the  first  specimen  of 
Melanocetus  johnsonii,  obtained  from  off  Madeira,  had 
engorged  another  fish  about  twice  its  own  length.  Dr.  Gill 
writes  : — '  The  extensibility  of  the  jaws  and  connected 
parts  as  well  as  the  dilatability  of  the  cesophagus,  stomach 
and  integuments  enabled  the  captor  fish  to  accomplish 
this  feat ' — after  which  it  took  a  bait  and  was  caught. 
Another  curious  fish,  Linophryne  lucifer,  from  the  same 
locality,  came  to  be  known  by  coming  up  to  surface,  hoist 
on  its  own  petard,  having  swallowed  another  fish  longer 
than  itself. 

The  Struggle  for  Existence. — As  we  watch  the  drama 
from  year  to  year  we  see  ever-recurrent  situations.  The 
dramatis  personae  may  be  different,  but  the  situation  is 
the  same.  Among  the  most  familiar  of  these  situations 
are  the  various  forms  of  '  the  struggle  for  existence  ', 
which  we  use  as  a  formula  to  include  all  the  ways  in  which 
living  creatures  react  to  limitations  : — Animals  get  hungry, 
they  seek  their  food,  they  endeavour  to  catch  what  often 
endeavours  not  to  be  caught,  they  compete  with  others 
who  endeavour  to  catch  the  same  elusive  prey,  they  have 
also  to  keep  an  eye  on  those  who  are  seeking  to  catch  them 
while  they  are  trying  to  catch  something  else  ;  and  mean- 
while they  have  to  struggle  to  keep  their  foothold  amid  the 
storm  of  the  careless  physical  environment.  There  are 
also  struggles  for  mates  and  for  the  safety  of  offspring. 
Which  of  these  endeavours  is  the  struggle  for  existence  ? 
Each  and  all.  For  the  real  meaning  of  the  phrase  is  to  be 
found,  not  in  picturing  this  or  that  kind  of  struggle  or 
endeavour,  but  rather  in  the  general  idea  of  living  organisms 
asserting  themselves  against  limitations  and  difficulties, 
partly  no  doubt  due  to  their  immediate  competitors  of  the 


THE  DRAMA   OF  LIFE 


same  kin  or  even  family,  but  by  no  means  restricted  to  this. 
It  is  important  to  realize  the  variety  of  '  struggle  '- 
from  a  life  and  death  competition  around  the  platter  of 
subsistence  to  a   persistent  and  peaceful  endeavour  after 
well-being.     It  may  be  for  foothold,  for  food,  for  mates, 
or  on  behalf  of  the 
family.     It  may  be 

(1)  between  fellows 
of   the   same  kind, 

(2)  between  foes  of 
quite     different 
kinds,    or    (3)    be- 
tween   organisms 
and  their    physical 
surroundings,  i.e. 
between    Life    and 
Fate.      In  insisting 
on  this  multiplicity 
of     '  struggle ',     or 
reaction   against 
limitations    and 


FIG.  7. — Spectacled  Cobra,  Naja  tripudians, 
in  the  act  of  striking.  The  animal 
grows  to  a  length  of  5  feet.  (After 
Fayrer.) 


difficulties,  we  are 
keeping  close  to 
Darwin's  own  meaning,  for  he  wrote  : — 

'  I  should  premise  that  I  use  this  term  ['  struggle  for 
existence ']  in  a  large  and  metaphorical  sense,  including 
dependence  of  one  being  on  another,  and  including  (which 
is  more  important)  not  only  the  life  of  the  individual,  but 
success  in  leaving  progeny.' 

Let  us  take  a  few  illustrations  to  show  the  variety  of 
'  struggle  '.  The  competition  between  antagonistic  species 


20  THE  WONDER   OF  LIFE 

and  indirectly  between  members  of  the  same  species  is 
vividly  pictured  in  an  account  which  Mr.  Dean  C.  Worcester 
gives  of  a  recent  visit  to  Cavilli  Island,  one  of  the  Philip- 
pines. The  actors  were  the  red-legged  boobies  (Sula 
piscator),  related  to  the  British  gannet,  and  the  frigate- 
birds  (Fregata  aquila). 

'  Just  before  dusk,  as  we  were  leaving  for  the  steamer, 
we  witnessed  an  extraordinary  scene.  Large  numbers  of 
red-legged  boobies  which  had  apparently  been  fishing  all 
day,  began  to  return,  bringing  fish  to  their  nesting  mates 
and  to  their  young.  The  frigate-birds  promptly  formed  a 
skirmishing  line,  and,  singly  or  in  pairs,  attacked  all  comers, 
compelling  them  to  give  up  their  fish.  Some  of  the  boobies, 
possibly  sophisticated  individuals  which  had  learned  wis- 
dom by  experience,  actually  handed  their  fish  over  to  the 
frigate-birds  and  so  escaped  without  much  drubbing,  but 
less  experienced  or  more  obstinate  individuals,  which  at 
first  refused  to  disgorge,  were  vigorously  punished  until 
they  changed  their  minds  and  threw  up  their  fish  which 
were  most  adroitly  caught  in  the  air  by  their  piratical 
enemies.  In  one  instance,  two  frigate-birds  set  upon  a 
booby,  one  of  them  attacking  him  from  above,  and  the  other 
flying  below  to  catch  the  fish  which  he  dropped,  and  getting 
five  out  of  seven.  Soon  the  incoming  boobies  began  to 
arrive  in  flocks,  and  the  frigate  birds  were  not  able  to  set 
upon  them  all,  so  that  many  individuals  got  through  to 
the  island.  Once  among  the  trees  they  were  left  in  peace.' 

Captain  A.  R.  S.  Anderson  has  given  us  a  dramatic  picture 
of  an  extraordinarily  keen,  though  somewhat  one-sided, 
struggle  between  birds  and  bats.  The  scene  is  in  the  Far  East 
by  the  banks  of  the  river  Salween,  where  lime-stone  rocks 
rise  for  some  250  feet,  and  are  bored  by  caves  and  orna- 
mented by  Buddhistic  sculpture.  The  human  tenants  are 


JTIG.  8. — Large  Bats,  Noctules,  Vesperugo  noctula,  clustering  on  an  old  tree. 
21 


22  THE  WONDER   OF  LIFE 

long  since  sped,  and  the  caves  are  the  home  of  legions  of 
bats.  As  the  sun  is  setting  a  couple  of  falcons  come  over 
the  hill  and  fly  restlessly  to  and  fro  over  the  river,  keeping 
a  watchful  eye  on  the  mouths  of  the  caves.  Then  kites 
and  jungle  crows  gather  together  till  there  are  about  a 
hundred.  The  dramatic  moment  is  at  hand.  Out  comes 
a  single  bat,  then  a  pair,  in  puzzling  jerky  flight,  eluding 
the  birds  of  prey,  who  are  too  experienced  to  be  led  off  on  a 
profitless  pursuit.  There  is  a  pause  for  a  minute  or  two, 
then  a  sudden  rush  of  wings  is  heard,  and  the  nightly  sortie 
begins.  Like  smoke  from  a  dirty  chimney  on  a  stormy 
day,  the  bats  issue  in  a  dense  column,  ten  feet  wide  by  ten 
feet  deep,  in  hundreds  and  thousands,  so  closely  packed 
that  many  are  jostled  into  the  river  below.  The  falcons, 
kites,  and  jungle  crows  have  now  their  innings  ;  they  fall 
upon  the  sortie  and,  striking  right  and  left,  soon  obtain  all 
they  want.  But  the  enormous  majority  of  the  bats  escape 
safely  into  the  after-glow.  It  seems  likely  that  the  cease- 
less sifting  process  is  automatically  regulated,  else  the 
relatively  weak  and  slowly  reproducing  race  of  bats  would 
long  since  have  come  to  an  end.  Bats  have  such  an  unpre- 
dictable kind  of  flight  that  they  are  very  difficult  to  catch  ; 
when  the  birds  reduce  their  numbers  so  that  the  crowd  is 
no  longer  closely  packed,  the  nightly  percentage  of  victims 
will  fall.  It  will  no  longer  pay  the  birds  to  hunt  them, 
and  there  will  be  a  close  time  till  the  numbers  rise  again. 
A  New  Jersey  naturalist  describes  a  great  host  of  mos- 
quitoes, which  were  pursued  and  thinned  by  a  large  army 
of  dragon-flies,  which  were  being  in  turn  destroyed  by  a 
big  flock  of  birds.  Similarly  in  mankind,  while  one  tribe 
is  destroying  another  a  more  civilized  power  often  bears 
down  upon  the  conquerors.  We  have  referred  elsewhere  to 


THE  DRAMA   OF  LIFE  23 

Mr.  Hudson's  very  instructive  picture  of  a  wave  of  life  in 
South  America.  Fine  weather  and  many  blossoms  ;  many 
flowers  and  many  bees  ;  many  bee-grubs  and  many  mice  ; 
multitudes  of  mice  and  a  thronging  host  of  birds  of  prey. 
Diets  are  changed,  habits  are  changed,  numerical  propor- 
tions are  changed  ;  and  then — the  season  suddenly  changes, 
and  everything  collapses  with  terrific  mortality  into  a  new 
position  of  equilibrium. 

Rotifers,  or  Wheel-animalcules,  are  microscopic,  but  the 
struggle  for  existence  is  as  keen  as  among  rats.  Most  eat 
single- celled  plants  and  animals ;  some  pierce  the  cells  of 
Algee  and  suck  out  the  living  matter ;  and  some  swallow 
other  Rotifers  whole.  Mr.  C.  F.  Rousselet,  whose  beautiful 
microscopic  preparations  of  Rotifers  are  deservedly  famous 
both  in  Europe  and  America,  has  told  us  of  the  cannibalistic 
voracity  of  Ploesoma  hudsoni,  which  seems  actually  to 
have  a  predilection  for  its  own  kith  and  kin.  '  Of  all 
Rotifers  this  is  the  most  vigorous  swimmer ;  it  rushes 
through  the  water  at  great  speed,  snapping  at  any  other 
Rotifer  that  conies  in  its  way,  carrying  it  in  its  mouth 
and  devouring  it  without  a  moment's  pause '.  '  The 
attacking  individual  snaps  at  and  holds  on  to  its  victim  like 
a  bull- dog  ',  it  pierces  the  skin  and  sucks  up  the  soft  parts. 
One  of  Mr.  Rousselet's  slides  showed  three  of  these  '  atro- 
cious cannibals  '  :  '  the  anterior  individual  is  being  carried 
in  the  jaws  of  its  captor,  whilst  the  latter  has  been  caught 
a  moment  later  by  a  third  Ploesoma,  intent  on  devouring 
both '.  We  have  here  a  good  instance  of  the  frequent 
intensity  of  the  struggle  for  existence. 

Thrust  and  Parry. — We  get  a  side-light  on  the  struggle 
for  existence  when  we  observe  the  prevalence  of  armour 
and  weapons,  and  all  manner  of  defensive  and  offensive 


24  THE  WONDER  OF  LIFE 

devices.  We  say  '  armour  ',  and  we  see  armadillos  in  their 
bony  mail,  giant  sloths  with  shields  an  inch  in  thickness, 
tortoises  almost  invulnerable,  scale-clad  fishes,  molluscs 
in  their  shells,  crustaceans  and  insects  within  their  strong 
chitinous  cuticles,  sea-urchins  bristling  with  heavy  spines 
like  hedgehogs, — the  stage  is  full  of  men  at  arms. 

We  think  of  '  weapons  ',  and  what  a  collection  rises  into 
view,  from  the  microscopic  stinging  threads  of  the  jelly- 
fish and  the  Portuguese  man  of  war  to  the  tusk  of  the  male 
narwhal,  ten  feet  long,  from  the  forceps  of  crabs  to  the 
antlers  of  stags,  from  the  stings  of  bees  to  the  fangs  of  the 
cobra,  from  the  lashing  tail  of  the  sting-ray  to  the  sword 
of  the  sword-fish,  from  the  strangling  arms  of  the  octopus 
to  the  talons  of  the  eagle  ! 

But  stopping  an  endless  catalogue,  let  us  take  three  or 
four  instances  of  the  quaintness  of  methods  of  offence  and 
defence. 

In  the  case  of  the  common  nettle,  the  sting  is  effected  by 
specialized  hairs,  each  of  which  shows  a  bulbous  base  with 
glandular  cells,  a  slender  stalk  with  a  duct  running  up  it, 
and  a  sharp-pointed '  cap  '  at  the  end  of  the  brittle  tip.  The 
sharp  tip  pierces  the  skin,  and  in  breaking  off  there  effects 
an  injection  of  the  poisonous  secretion.  In  the  hair  of 
the  Chilian  nettle  (Loasa)  there  is  no  cap  to  the  hair,  the 
tip  is  sharp-pointed  and  like  a  curved  needle. 

A  very  curious  means  of  defence  is  seen  in  a  number  of 
Holothurians,  or  sea-cucumbers,  which  discharge  long 
glutinous  threads,  or  '  Cuvierian  organs  '  from  the  posterior 
end  of  the  body.  In  Holoihuria  nigra,  the  Cuvierian  organs 
are  white  conical  bodies  which  are  protruded  posteriorly, 
when  the  creature  is  irritated.  They  remain  attached  by 
their  bases  to  the  animal,  but  elongate  into  long  glutinous 


THE  DRAMA  OF  LIFE  25 

tubes  which  become  disconnected.  The  elongation  is  due 
to  internal  fluid  pressure  and  is  always  preceded  and  accom- 
panied by  a  rise  of  pressure  in  the  fluid  of  the  body-cavity. 
A  lobster  of  considerable  size  may  be  bound  hand  and  foot 
with  these  threads  of  the  '  cotton  spinners ',  as  some 
of  the  Holothurians  are  called,  a  quaint  instance  of  an 
animal  with  a  highly  developed  nervous  system  being 
ensnared  by  the  retaliations  of  a  creature  which  has  not 
a  ganglion  or  nerve-centre  in  its  whole  body.  How  dim 
its  awareness  of  the  situation  must  be  ! 

As  Dr.  Theodore  Gill  observes,  the  capture  of  fishes  by 
a  lure  began  long  before  man  acquired  that  art,  it  was 
evolved  among  fishes  themselves.  The  angler  (Lophius 
piscatorius]  has  a  dorsal  fin- ray  turned  into  a  rod  and  line 
and  dangling  bait.  '  It  needs  no  hook,  for  the  bait 
attracts  a  victim  sufficiently  near  to  be  seized  upon  by  the 
sudden  leap  of  the  angler '.  The  dangling  of  the  bait  is 
quite  automatic,  and  the  device  probably  began  fortuitously, 
but  the  angler  is  very  alert.  In  some  Deep-Sea  anglers  there 
is,  in  addition  to  wormlike  baits,  a  phosphorescent  bulb 
or  lantern  which  is  perhaps  seductive. 

Many  butterflies,  especially  from  warm  countries,  have 
the  power  of  exhaling  a  repulsive  odour.  Dr.  P.  A.  Dixey 
mentions  Acraea,  Euploea,  and  Papilio  as  genera  among 
which  this  property  is  common.  '  Musty  straw,  stable 
litter,  rabbit-hutches,  acetylene,  bilge-water,  these  are  some 
of  the  substances  to  which  the  odours  of  these  unsavoury 
butterflies  have  been  compared '.  The  odour  may  be 
distributed  from  patches  of  specialized  scales  or  hairs,  or 
from  the  general  wing  surface,  but  never  from  plume-scales 
such  as  distribute  the  delicate  flower-like  perfumes.  More- 
over the  scents  occur  in  both  sexes  and  may  be  stronger 


26  THE  WONDER  OF  LIFE 

in  the  female.  There  is  much  actual  evidence  that  the 
repulsive  odour  protects  the  butterflies  from  insect-eating 
enemies.  Dr.  F.  A.  Dixey  notices  that  many  of  them  are 
conspicuous,  slowly-flying  forms,  given  to  courting  obser- 
vation rather  than  to  avoiding  it.  They  trust  to  their 
repulsiveness. 

'  Moreover  since  it  is  well  recognized  that  the  preservation 
of  the  life  of  the  female  is  more  important  than  that  of  the 
male  for  the  welfare  of  the  species,  we  should  expect  that 
if  there  is  a  difference  between  the  sexes  in  the  intensity  of 
the  odour,  that  difference  would  be  in  favour  of  the  female. 
This,  again,  is  borne  out  by  observation  in  a  number  of 
cases.  Where  both  sexes  are  repulsive,  the  female,  as  a 
rule,  is  the  more  repulsive  of  the  two,  and  therefore  (as  a 
consolation)  the  safer  from  attack.' 

Many  Inventions. — In  the  higher  reaches  of  the  animal 
kingdom  we  find  examples  of  deliberate  device — the  cat 
watches  for  the  mouse,  or  the  fox  for  the  rabbit,  the  ele- 
phant bides  his  time  and  has  his  revenge  after  many  days, 
the  wolves  encircle  their  victim  and  close  in  upon  him ; 
wits  are  pitted  against  wits  in  the  battle  of  life.  At  lower 
reaches  we  find  instinctive  inventions  which  work  extra- 
ordinarily well,  but  which  do  not  seem  to  require  any 
deliberate  control.  It  is  possible  that  they  are  suffused 
with  awareness,  but  their  efficient  performance  depends 
on  the  inherited  organization  of  the  nervous  system.  The 
insect  '  feigning  death '  is  certainly  not  consciously  trying 
to  efface  itself ;  the  crab  that  covers  itself  with  a  disguise 
of  foreign  objects  is  not  clear  as  to  its  own  device  (we 
shall  discuss  the  case  later  on),  for  it  has  been  known  to 
put  on  a  transparent  cloak  with  which  the  experimenter 
provided  it.  In  many  cases,  doubtless,  intellectual  pro- 


THE  DRAMA   OF  LIFE  27 

cesses  which  have  their  seat  in  the  higher  centres  of  the 
brain  may  come  to  the  aid  of  the  inborn  instinctive  pro- 
cesses which  are  localized  in  lower  centres.  And  apart 
altogether  from  intelligence  and  instinct  there  are  many 
striking  cases  of  what  may  be  metaphorically  called  suc- 
cessful inventions  or  '  shifts  for  a  living  ',  which  depend  on 
structural  peculiarities  of  the  organism  gradually  perfected 
through  the  ages.  Without  seeking  to  analyse  at  this 
stage,  we  wish  to  notice  some  of  these  life-saving  and  life 
furthering  adaptations  of  structure  and  behaviour,  which 
it  is  one  of  the  charms  of  Natural  History  to  discover.  Just 
as  in  the  human  drama  we  see  disguise  and  mask,  imitation 
and  bluff,  underhand  devices  and  clever  escapes,  so  it  is 
in  the  animal  world,  though  the  psychology  of  the  matter 
is  in  most  cases  entirely  different. 

Over  and  over  again  in  the  history  of  animal  life  the 
situation  has  been  saved  by  some  thorough  change  (which 
doubtless  took  time  to  effect)  in  habitat  or  habit.  The 
earthworms,  springing  probably  from  an  aquatit  stock, 
discovered  the  subterranean  world,  and  must  have  enjoyed 
a  prolonged  golden  age  beneath  the  ground,  until  centipedes, 
burrowing  beetles,  and  eventually  moles  came  to  trouble 
them  in  their  deep  retreats.  A  temporary  prosperity  must 
have  likewise  rewarded  the  invasion  of  the  air  by  insects, 
— until  flying  reptiles,  birds,  and  bats  discovered  the  secret 
as  well ;  or  the  adoption  of  a  marine  habit  by  the  ancestors 
of  our  modern  Cetaceans,  Pinnipeds,  sea-turtles,  and  sea- 
snakes.  What  success  must  have  rewarded  the  birds' 
discovery  of  migration,  or  the  hibernating  mammals'  very 
different  device  of  evading  the  hardships  of  winter !  In 
hundreds  of  different  ways,  at  point  after  point,  life  has 
saved  the  situation  by  a  change  of  tactics. 


28  THE  WONDER   OF  LIFE 

A  general  resemblance  to  surroundings  is  often  life- 
saving,  and  one  must  not  be  in  haste  to  exclude  the  possi- 
bility that  some  animals  actively  seek  out  the  surroundings 
with  which  they  best  harmonize.  With  certain  backgrounds 
a  woodcock  or  a  curlew  upon  its  nest  fades  into  its  sur- 
roundings and  becomes  practically  invisible,  just  as  does 
the  brown  lizard  on  the  sand,  the  green  snake  among  the 
branches,  the  transparent  arrowworm  in  the  sea,  the 
mountain  hare  among  the  snow,  the  hare  on  the  ploughed 
land, — and  one  might  fill  a  page  with  good  examples. 

It  has  been  noticed  that  a  grey  donkey  in  a  field  at  night 
may  be  quite  invisible  at  a  distance  of  a  few  yards,  though 
the  noise  of  its  cropping  is  very  distinct.  On  a  night  with 
diffused  ground  light,  when  cows  were  visible  at  a  distance 
of  eighty  yards,  a  donkey  was  quite  invisibla  at  eight.  It 
is  probable  that  his  lighter  under-surface  served  to  diffuse 
what  light  there  was.  A  careful  observer  writes  : — 

'  On  his  starboard  quarter  at  four  yards  distance,  his  dark 
head  appeared  as  a  moving  blur,  but  "  stern  on  "  at  that 
distance  he  was  completely  invisible — an  "  airy  nothing  " — 
though,  like  Polonius,  "  at  supper  ".  It  was  most  extra- 
ordinary to  hear  the  animal  feeding  and  to  be  unable  to  see 
a  vestige  of  him.' 

There  is  an  interesting  moth,  the  Golden-Eight  moth 
(Plusia  nwneta),  which  during  the  last  half-century  has  been 
spreading  westward  and  southward  from  its  Russian  head- 
quarters. Its  first  appearance  in  Britain  was  in  1857 ;  a 
great  invasion  occurred  in  1890  ;  since  then  it  has  diffused 
itself  over  England.  It  is  called  '  Golden  Eight '  because 
of  the  markings  on  its  golden-grey  wings.  When  it  is  at 
rest,  however,  it  puts  on  the  mantle  of  invisibility  and 


THE  DRAMA   OF  LIFE 


29 


strongly  resembles  a  dead 
and  dry  leaf  still  attached 
to  the  stem.  Mr.  Charles 
Nicholson  writes  : — 


—  c 


' The  front  legs  are 
stretched  out  straight  in 
front  of  the  head  at  a  right 
angle  to  the  axis  of  the 
body,  the  second  pair  of  legs 
being  pressed  close  to  the 
body,  while  the  last  pair 
just  hold  to  the  support, 
almost,  or  quite,  covered 
by  the  tips  of  the  fore 
wings  which  just  touch 

beyond  the  body,  the  FlG-  9.— Piece  of  Figwprt,  Scro- 
moth  appearing  to  be 
clinging  to  its  support  by 
the  front  legs  and  wings 
only.  It  falls  to  the 
ground  when  touched.' 


phularia  nodosoa,  with  pupa- 
cases  (c)  of  a  beetle,  Oionus 
scrophularice,  with  a  marked 
superficial  resemblance  to  the 
fruits  (F). 


The  value  of  the  protective  coloration  may  be  enhanced 
when  it  is  associated  with  a  power  of  colour- change,  when 
the  animal,  within  certain  limits,  can  adjust  itself  to  the 
particular  hue  or  even  pattern  of  its  surroundings.  This 
is  extraordinarily  well  illustrated  by  many  of  the  flat-fishes, 
of  the  plaice,  flounder,  sole  series,  which  can  adjust  the 
shade  and  the  pattern  of  their  upturned  surface  so  that 
they  become  practically  part  and  parcel  of  the  sand  or 
gravel  on  which  they  are  resting.  It  appears  that  the 
colour  of  the  surroundings  first  affects  the  eye,  then  the 
brain,  then  the  sympathetic  nervous  system,  then  the 


30  THE  WONDER  OF  LIFE 

spinal  nerves  to  the  skin,  and  finally  the  state  of  con- 
traction of  the  pigment  cells  just  below  the  surface.  Any 
one  may  see  a  lemon-sole,  for  instance,  putting  on  its  gar- 
ment of  invisibility.  Until  one  catches  sight  of  its  eyes, 
it  seems  to  be  completely  lost  in  its  background.  The 
invisibility  is  sometimes  further  ensured  by  a  dusting  of 
sand,  but  it  is  remarkably  complete  without  that. 

It  may  be  explained  that  the  outer  skin  or  epidermis 
of  fishes  is  delicate  and  transparent.  All  the  colour  is  in 
the  dermis,  and  it  usually  occurs  in  remarkable  pigment- 
cells  or  chromatophores.  These  typically  show  numerous 
radiating  processes,  and  the  pigment  can  be  spread  out 
to  the  periphery  or  concentrated  in  the  centre,  according 
to  the  expansion  or  contraction  of  the  mobile  protoplasm 
of  the  pigment-cell.  According  to  the  pigment  which 
they  contain — black,  yellow,  red,  and  so  on — the  pigment- 
cells  are  called  melanophores,  xanthophores,  erythrophores, 
and  so  forth.  Then  there  are  other  cells  containing  spangles 
of  the  waste-product  guanin,  which  are  called  iridocytes  or 
guanophores.  They  cause  the  silvery,  metallic,  or  iridescent 
appearance  familiar  on  many  fishes.  Professor  Ballowitz 
has  recently  discovered,  in  the  Weaver  and  some  other 
Bony  Fishes,  a  new  kind  of  chromatophore,  consisting  of  a 
group  of  cells — a  cluster  of  iridocytes  with  an  encapsuled 
central  melanophore  which  sends  its  ramifying  process 
through  the  capsule  in  complicated  courses. 

The  story  goes  that  a  chameleon,  whose  power  of 
colour-change  is  famous,  reached  the  limit  of  its  capacity  for 
*  sympathetic  coloration  '  when  it  was  placed  in  a  tartan- 
lined  box.  It  soon  died,  with  a  pained  expression  of  baffled 
adaptability,  but  some  of  the  achievements  of  flat-fishes 
in  the  way  of  harmonizing  with  their  surroundings  do  not 


FIG.  10.— Flat  Fish,  Rhomboidichthys  podas.    After  resting  for  two 
or  three  days  on  fine  gravel.    (After  Sumner.) 


FIG.   10A.— Flat  Fish,  Rhomboidichthys  podas.     After  resting  for 
three  days  on  the  spotted  background.     (After  Sumner.) 


«€.£9**«ft*1 


ti»  *****  jrf  con- 
ta*  fturiiww,    Any 
tvfetancr.  putting  on  its  gar- 
'«»;  catebvtf  agiit  of  it»  eyes, 
;-*r  »••  ite  background.    The 
;  *urt4*«r  easored  by  a  dufliiug  of 
ow}  iol  gniJ 


ft  no  8y«b 

t^.  -•«  ..r,t      All  the  colour  is  in 

ha   •-f-rr(arkablc  pigment- 

-iily  show  numerous 

'   can  be  spread  out 

j>  thr  centre,  according 

•\r,-  ..f<li{^    t-*>  the  pigment  which 
-r  i.  •••*ttB»w.  r«i.  andao  oo  —  the  pigment- 
-  »>  -j  -^b»i?na,  xAtir-hoplivres,  crythrophores, 
.-M»  are  other  c-el  is  •«.-;.: 
u.  which  au>  ca!' 
ii.;-  .jiivet-y.  u 
T-  many  fishes. 

in  the  Weaver  and  some  other 

;if  chroinatophore,  consisting  of  a 

.'fiboq 


$e    power    of 

•  . 

:  an- 

vements  of  fiat-fisheg 

.urroundings  d<> 


THE  DRAMA   OF  LIFE  31 

fall  far  short  of  the  tartan  standard.  We  have  inserted 
two  illustrations  which  show  how  extraordinarily  close  the 
approximation  may  be. 

The  protective  value  of  a  colour-resemblance  between  an 
animal  and  its  surroundings  is  probably  increased  when  the 
form  and  pose  of  the  creature  is  like  something  else.  We 
do  not,  however,  know  very  much  in  regard  to  the  degree 
of  attention  which  the  enemies  of  these  protected  animals 
pay  to  form.  As  many  animals  appear  to  be  alert  in  de- 
tecting movements  of  their  prey,  there  will  be  an  advantage 
if  the  latter  are  shaped  like  other  things.  A  walking-stick 
insect  that  is  creeping  or  swaying  about  on  a  twig,  will  be 
less  likely  to  be  seen  as  a  moving  object  because  of  its 
strong  form-resemblance  to  a  group  of  twigs. 

Here  we  have  the  well-known  cases  of  butterflies  like 
leaves,  of  caterpillars  like  little  twigs,  of  spiders  like  lichens, 
and  so  on.  It  is  interesting  to  notice  that  the  perfection 
of  the  resemblance  is  often  due  to  combination  of  items. 
Thus  in  the  famous  case  of  Kallima,  which  is  like  a  pendent 
withered  leaf  when  it  settles  down,  usually  head  down- 
wards, on  a  branch,  there  is  similarity  in  colouring,  there  is 
resemblance  in  shape,  the  mid-rib  and  veins  of  the  leaf  are 
counterfeited  by  the  nervures  of  the  wings,  the  likeness 
is  heightened  by  marks  on  the  wings  which  look  like 
fungus  marks  on  the  leaves,  and  so  on.  Moreover,  in 
Kallima  there  is  much  individual  variation  in  the  markings 
on  the  under  surfaces  of  the  wings,  '  simulating  all  degrees 
of  decay  and  discoloration  and  fungus  attack '.  It  seems 
reasonable  to  suppose  that  this  variability  of  pattern  is 
even  more  effective  than  if  the  Kallima  were  tied  down  to 
resembling  only  one  kind  of  withered  leaf. 

Subtlest  of  all  these  misleading  resemblances  to  other 


32  THE  WONDER   OF   LIFE 

things  is  mimicry  in  the  strict  sense,  where  there  is  a  striking 
external  resemblance  between  two  unrelated  animals  which 
frequent  the  same  haunts.  As  examples  we  may  cite  the  re- 
semblance between  the  drone-fly  (Eristalis)  and  a  bee ; 
between  the  European  grass-snake,  Tropidonotus  viperinus, 
quite  innocent  in  character,  and  a  viper  ;  between  the  Lepi- 
dopteron  Trochilium  apiforme  and  the  hornet ;  between  a 
spider  (e.g.  Myrmarachne  formicaria]  and  the  dreaded  ant. 

It  is  usual  to  refuse  the  title  of  true  mimicry  unless  it 
can  be  shown  (or  unless  it  has  been  shown  in  analogous 
cases)  that  the  mimicker  lives  along  with  the  mimicked 
to  a  considerable  extent,  that  the  mimickers  are  in  the 
minority,  that  the  mimickers  are  like  the  mimicked  in 
superficial  characters  only,  and  that  the  mimicked  are 
more  or  less  markedly  safe  and  usually  more  or  less  con- 
spicuous. It  goes  without  saying  that  the  use  of  the  terms 
mimicker  and  mimicked  is  entirely  metaphorical,  for  the 
mimetic  resemblance  is  not  deliberate. 

Students  of  mimicry  are  accustomed  to  distinguish  several 
types.  Thus  in '  Batesian  Mimicry  ',  first  clearly  defined  by 
the  naturalist-traveller  Bates,  we  have  a  palatable  animal 
escaping  in  virtue  of  its  superficial  resemblance  to  unpalat- 
able forms,  with  striking  features,  which  are  rarely  attacked 
and  are  greatly  in  the  majority  over  the  mimickers.  The 
bad  reputation  of  ants  gives  a  vicarious  safety  to  several 
ant-like  spiders ;  the  disagreeable  taste  of  the  mimicked 
butterfly  helps  the  survival  of  its  palatable  Doppel- 
Ganger. 

Mr.  Guy  A.  K.  Marshall  observed  a  Dipterous  fly,  Ceria 
gambiana,  visiting  flowers  in  company  with  a  formidable 
wasp,  Polistes  marginalis,  and  it  seems  reasonable  to  infer 
that  the  fly  profits  by  its  likeness  to  the  dangerous  creature 


1 1 . — A.  A  butterfly  (Kallima  inachis),  with  outspread  wings 
showing  the  upper  surface.  B.  The  same  on  a  branch,  head 
downwards,  with  the  wmgs  folded  together,  showing  the  under 
surface.  C.  A  withered  leaf  hanging  downwards. 


THE  WONDER  OF   UF£ 

ifry  ia  the  strict  senae,  ^  &  a 

:rri>U*»\X'  between  two  it--. 
«t«w  kaonts.    As  «MMm:*w  w-  i      !i*»  re- 

t^wwn  fche  drojte-rl  •>  bee ; 

K^^ipyan  grass-sruikf.    '  :inu,9, 

st  i»  character,  and  A  vipwr ;  i^xween  the  Lepi- 
o^4lf«m  api/orww  *n«J  th«  bomot ;  between  a, 
Ifftnwrockne  formicaria }  *IM!  the  dreaded  ant. 
to  refuse  the  title  oi  t.r»  Biimicry  unless  it 

Ho^tt  for  ujiless  it  haw  »n  in  analogous 

-.!!  .01 


r  fess  marketUy  safe  and  usviaUv  more  or  less  con- 
j.oa.'*.     It  goes  without  saying  that  the  use  of  the  terms 

ienefeor  and  mimicked  is  entirety  nv  ,  for  the 

?:«?Sf^At  resemblance  is  not  deliberate, 

..ft-  of  mimicry  are  accustomed  to  disti 
t  ypivp      1  h«s  in '  Batesian  Mimicry  ',  fi rat  cl»'-. 
ik*1  tiataraEst-traveller  Bates,  we  have  a  palatable  animal 
raping  in  virtue  of  its  superficial  rew  unpalat- 

able forma,  with  striking  features,  winch  are  rarely  attacked 
and  are  gr**tly  in  the  nmj  .  the  niiinickers.     The 

bad  reputation  <  .     ;  i  >us  safety  to  several 

ant-like  spiders ;   the  di«rag»*«nbk.'  taste  of  the  mimicked 
butterfly   helps  datable   Doppel- 

0  anger, 

Mr.  Guy  '•  pte   i 

yambiana,  viairmg  flowers  i 
wasp.  "rgmalis,  a\ 

that  t'  ;s  by  its  lik  , 


— B 


THE  DRAMA   OF  LIFE  33 

with  a  bad  reputation  that  it  has  come  to  associate  with. 
In  all  such  cases  single  observations  are  unconvincing,  but 
when  similar  cases  accumulate  the  argument  gathers  force. 
Thus  it  is  very  interesting  that  J.  Bourgeois  should  have 
noticed  Ceria  conopsoides  visiting  the  wounds  on  the  trunk 
of  a  horse-chestnut  in  company  with  a  wasp,  Odynerus 
crassicornis,  a  formidable  insect.  Both  were  visiting  the 
tree  with  the  same  end — to  lick  the  exudation ;  the  fly 
was  probably  protected  from  certain  enemies  by  its  '  Bate- 
sian  mimicry '  of  the  wasp. 

Another  type  of  mimicry  is  called  Miillerian,  after  the 
naturalist  Fritz  Miiller,  and  here  we  have  a  resemblance 
between  several  immune  species  living  in  the  same  country. 
This  is  well  illustrated  among  South  American  Lepidoptera, 
e.g.  Danaids,  Heliconids,  and  Acrseids,  and  it  seems  to 
work  like  a  sort  of  mutual  assurance.  None  are  palatable, 
but  by  being  like  one  another  they  spread  the  risk  of  being 
experimented  on  by  inexperienced  birds.  Birds  have  to 
learn  discretion  in  their  youth  ;  they  take  many  an  unpleas- 
ant bite  of  unpalatable  victims  before  they  become  pro- 
ficient ;  they  remember  the  marks  of  bad  taste,  and  the 
more  similar  these  marks  are  the  more  likely  their  possessors 
are  to  escape.  The  more  in  the  ring,  the  less  the  waste  of  life. 

There  are  many  difficulties  in  connexion  with  mimicry — 
especially  perhaps  the  question  of  its  evolution — but  it  is 
difficult  to  see  the  remarkable  illustrations  collected  by 
Professor  Poulton  and  to  consider  the  facts  he  adduces 
as  to  its  efficacy  in  certain  cases,  without  being  ready  to 
admit  that  it  plays  a  considerable  and  curious  part  in  the 
drama  of  animal  life. 

Sometimes  the  mimicry  is  very  exact  as  regards  colouring 
and  pattern ;  sometimes  it  is  rather  in  pose  and  movement, 

D 


34  THE  WONDER  OF  LIFE 

Let  us  take  an  instance.  From  a  pale  emerald-green  nest, 
sent  from  the  Gold  Coast  to  the  Zoological  Society  in  London, 
there  emerged  a  crowd  of  young  Mantids,  about  four  milli- 
metres in  length,  which  exhibited  a  curious  mimicry. 
'  When  crawling  about  the  case  they  looked  exactly  like 
a  crowd  of  busy  ants,  their  rapid  darts  and  pauses  recalling 
irresistibly  the  busy  method  of  progression  so  characteristic 
of  these  Hymenoptera  '.  Now,  there  is  nothing  more  pro- 
fitable for  an  innocent  little  insect  than  to  be  like  an  ant, 
for  ants  have  a  very  bad  reputation,  or  what  corresponds 
in  the  animal  world  to  a  reputation.  But  the  interesting 
point  which  was  noticed  by  Mr.  R.  I.  Pocock,  the  Superin- 
tendent of  the  Gardens,  was  this,  that  it  was  only  when  they 
were  moving  about  that  they  resembled  ants.  When  they 
settled  down  they  were  seen  in  their  true  colours — as 
Mantises, '  raising  the  fore  part  of  the  body  and  head,  folding 
up  their  fore-legs,  and  every  now  and  then  swaying  gently 
from  side  to  side  as  if  rocked  by 
the  wind.  While  thus  employed 
they  were  seen  to  be  procrypti- 
cally  coloured  '.  That  is  to  say, 
they  were  inconspicuous.  This  is 
obviously  a  very  interesting  case  ; 
when  the  little  creatures  were 
resting  they  were  hidden,  and 
when  they  were  poking  about 
they  were  like  ants !  Without 
observations  and  experiments  in 
their  natural  surroundings  no 
naturalist  could  assert  that  the 
FIG.  12. — Spider,  Synemo-  young  Mantises  are  saved  from 

syna    formica,   like    an        ... 

ant.    (After  Peckham.)    elimination  by  being  inconspicu- 


THE  DRAMA   OF  LIFE  35 

ous  or  by  being  like  ants.  But  as  we  have  experimental 
proof  in  a  few  analogous  cases,  it  seems  quite  sound  Biology 
to  say  that  these  little  Mantises  probably  get  on  very 
much  better  because  they  have  added  to  the  usual  incon- 
spicuousness  of  their  kind,  the  additional  advantage  of 
being  like  ants  when  they  are  young.  For  by  the  time 
they  had  attained  a  length  of  seven  millimetres,  they  had 
lost  their  ant-like  look. 

Another  '  device  '  is  that  of  masking,  where  the  creature 
disguises  its  real  nature  by  covering  itself  with  foreign 
bodies.  It  is  difficult  to  draw  the  line  between  extrinsic 
armour  and  disguise.  Thus  the  larval  caddis-insects  in 
the  streams  cover  themselves  with  minute  pebbles  or  with 
pieces  of  plant-stem  and  the  like  ;  and  this  is  probably  in 
the  main  a  protection,  not  a  mask.  When  we  pass  to 
crabs  covering  themselves  with  sea- weed,  or  with  sponge, 
or  with  hydroids,  or  with  part  of  a  sea-squirt's  tunic,  we 
have  to  do  with  something  nearer  masking. 

Zoologists  are  well  aware  that  the  little  crabs  of  the 
genus  Cryptodromia  are  in  the  habit  of  masking  themselves 
with  pieces  of  sponge  or  ascidian  or  the  like.  R.  P.  Cowles 
has  recently  watched  the  whole  process  of  sponge-cutting. 
The  naked  crab  (Cryptodromia  tuberculata,  in  the  Philip- 
pines) cuts  a  groove  on  an  encrusting  grayish  sponge, 
works  its  way  under  it,  and  dislodges  it.  In  a  short  time 
the  ragged  edges  of  the  sponge  shield  grow  smooth  and 
neat.  The  cutting  is  done  with  the  forceps,  but  the  dis- 
lodged piece  is  caught  hold  of  and  carried  by  the  last  pair 
of  legs. 

'  It  is  a  surprise  to  the  collector  when,  on  turning  over  a 
rock  covered  with  large  and  small  patches,  he  sees  some  of 


36  THE   WONDER  OF  LIFE 

the  smaller  patches  suddenly  become  animated  and  crawl 
away.  Another  surprise  is  in  store  for  him  when  he  picks 
up  one  of  these  small  patches  and  finds  it  to  be  the  cover 
of  a  crab  carefully  hollowed  out  so  as  to  fit  the  outline  of  the 
carapace,  and  tightly  held  in  place  by  the  last  pair  of 
legs,  whose  dactyli  [terminal  joints]  are  hooked  into  the 
inturned  rim.' 

Mr.  Cowles  also  describes  the  way  in  which  the  Pistol 
Crab  (Alpheus  pachychirus)  of  the  Philippines  makes  its 
tube  of  matted  Alga-threads.  The  tubes,  which  are  rather 
shelters  than  masks,  are  often  25  to  30  centimetres  long  and 
2  centimetres  in  diameter,  and  one  end  is  fixed  to  the  rock. 
A  male  crab  placed  on  a  piece  of  matted  Alga  turned  itself 
on  its  back,  and  using  the  slender  chelate  limbs  imme- 
diately behind  the  forceps,  drew  the  sides  of  a  furrow  to- 
gether and  sewed  them  by  a  simple  stitching.  Threads  of 
Alga  were  drawn  from  each  side  into  the  opposite  side. 
On  another  occasion  a  tube  was  torn  into  shreds  and  given 
to  a  pair  of  crabs,  who  made  a  coherent  tube  by  next  morn- 
ing. Filaments  were  entangled  on  the  edges  of  a  sheltering 
piece  of  rock  and  then  drawn  together. 

'  When  the  Alpheus  found  a  hole  in  the  rapidly  forming 
tube,  the  slender  legs  came  through,  caught  hold  of  the 
filaments  of  the  Alga,  and  manipulated  them  in  much  the 
same  manner  as  a  man  might  the  thread  with  which  he 
darns  a  hole  in  his  sock  ;  that  is,  by  drawing  the  edges  of 
the  hole  together  and  fastening  them.' 

Self-Advertisement. — In  great  contrast  to  those 
animals  that  walk  delicately,  or  lie  low,  or  fade  into  their 
surroundings,  or  put  on  disguise,  there  are  those  that  are 
noisy  and  bold,  fussy  and  conspicuous — the  self -advertisers. 


36  r 

the  smatt*  >•*«••  *-.*  |  *te*fttasi  wsd  crawl 

away.     *r  *    ^  £•*  fe*J3*  wto»  i»  picks 

up  on*"  •?  a"  ^°  be' t?tt!  cover 

of  a  cr*fc  &i  §L  **  to  fct  *fae  outhne  of  the 

cftrs»p«/«.  -wiS  8T  »y  the  last  pair  of 

Itjw  'Lf,;4  i  are  hooked  into  the 


§   $     -ay  in  which  the  Pistol 
==  5  vines  makes  its 

3         ,tbes,  which  are  rather 
1 of          -  centimetres  long  and 
71  d  is  fixed  to  the  rock, 
trotted  Alga  turned  itself 
~  j-          chelate  limbs  imme- 
5  sides  of  a  furrow  to- 
f        stitching.     Threads  of 
g*  S-       ''to  the  opposite  side. 
tub*}aV^ft-torn ;  riven 

who  mad  M  Inherent  t.i « o  ••  >m- 

•^.•jre  entai'.*"   £  ring 

•  •  8"  o 
59 

s.  ^  •  aing 

£.  '!_  .-at  hold  of  the 

—  ;n  in  much  the 

1  with  which  he 

ing  the  edges  of 
tj        ,orn.' 

j  their 


THE  DRAMA  OF  LIFE  37 

The  theory  is  that  those  in  the  second  set  can  afford  to  call 
attention  to  themselves,  being  unpalatable  or  in  some 
other  way  safe.  To  prove  a  theory  of  this  sort  is  impossible, 
but  it  becomes  cogent  and  convincing  in  proportion  to  the 
number  and  variety  of  cases  to  which  it  can  be  applied. 

Mr.  Pocock,  of  the  Zoological  Society's  Gardens  in  London, 
has  applied  the  theory  to  various  Mammals,  and  it  seems 
to  work  out  well.  Taking  the  common  shrew  (Sorex  vulgaris), 
for  instance,  he  points  out  that  it  is  fearless  and  careless, 


Fio.  14. — The  rattle  of  the  rattlesnake  (Crotalus),  composed  of  a  number 
of  horny  bells,  added  to  at  successive  moults.  It  is  agitated 
when  the  snake  is  excited  and  produces  a  shrill  noise.  Thus  large 
animals,  on  whom  the  snake  would  simply  waste  its  poison,  are 
warned  off. 


and  that  it  makes  a  frequent  squeaking  as  it  hunts.  It 
can  afford  to  be  a  self-advertising  animal  because  of  a 
strong  musky  scent,  which  makes  it  unpalatable.  A  cat 
will  never  eat  a  shrew.  The  odoriferous  glands  are  situated 
in  a  long  line  on  each  side  of  the  body.  Similarly,  the  large 
Indian  musk-shrew  (Crocidura  ccerulea)  is  conspicuous  even 
at  dusk,  quite  fearless  in  its  habits,  and  goes  about  making 
a  peculiar  noise  like  the  jingling  of  money.  But  it  is  safe  in 
its  unpleasant  musky  odour. 

The  common  hedgehog  is  comparatively  easy  to  see  at 
night ;  it  is  easy  to  catch,  because  it  stops  to  roll  itself  up, 
on  very  slight  provocation  sometimes  ;  it  rustles  about  in 


3  8  THE   WONDER  OF  LIFE 

the  herbage  and  '  sniffs  furiously  '  as  it  goes  ;  it  often  calls 
to  its  mate  ;  it  is  at  no  pains  to  keep  quiet.  Nor  need  it, 
for  although  a  few  enemies  manage  to  eat  it,  the  spines  are 
in  most  cases  quite  effective  prevention.  Moreover,  it 
can  give  rise  when  irritated  to  a  most  horrible  stench.  The 
porcupine  is  another  good  instance  of  a  self-advertiser, 
and  so  is  the  crab-eating  mungoose  (Mungos  cancrivora). 

In  a  few  cases  we  have  some  definite  knowledge  in  regard 
to  the  actual  process  of  adaptive  colour-change.  The  spotted 
salamander  (Salamandra  maculosa],  with  its  conspicuous 
livery  of  bright  yellow  and  dark  brown,  is  a  case  in  point. 
It  is  well  known  to  become  almost  black  when  the  soil  of 
its  vivarium  is  dark  and  relatively  dry.  Two  things 
happen :  the  yellow  areas  become  gradually  smaller,  re- 
treating towards  the  centre  till  they  disappear ;  and  the 
dark  areas  become  darker.  Experiments  following  the 
ordinary  method  of  exclusion  are  very  instructive,  e.g., 
using  a  black-paper  ground  with  the  normal  humidity. 
The  shrinkage  of  the  yellow  spots  is  induced  by  the  colour 
of  the  ground,  while  the  darkening  is  brought  on  by 
increasing  drought.  An  experimenter,  Alois  Gaisch, 
relates  that  he  put  a  salamander  into  a  vivarium  with 
black  peaty  soil  (which  remained  moist),  and  found  it 
almost  unrecognizable  after  three  months.  The  yellow 
spots  had  shrunk,  there  were  many  black  dots  about  their 
margins,  and  microscopic  examination  showed  that  the 
black  pigment  had  abundantly  invaded  the  yellow  areas. 
Two  other  salamanders  put  in  about  the  same  time  showed 
no  change  of  colour,  which  seems  to  show  that  there  are 
differences  in  individual  susceptibility.  If  that  be  so,  and 
if  it  had  not  to  do  with  age  or  the  like,  we  have  an  illustra- 
tion of  how  a  selective  process  might  work.  For  if  it  were 


THE  DRAMA  OF  LIFE 


39 


a  matter  of  great  advantage  that  yellow  and  black  salaman- 
ders should  lose  their  yellowness  in  a  black-soiled  coun- 
try, it  is  plain  that  the  non- susceptible  types  would  be 
eliminated,  while  the  susceptible  types  would  survive  and 
multiply  after  their  kind. 

We  are  accustomed  to  think  of  the  chameleon's  colour- 
change  in  connexion  with  protection,  but  it  seems  also 
to  have  a  distinctly  repellent  value.  Mr.  Cyril  Crossland 
has  given  an  animated 
account  of  a  chameleon 
frightening  off  a  fox 
terrier  which  attacked 
it.  At  first  the  reptile 
tried  to  run  away,  but 
that  is  not  its  strong 
point  !  '  In  a  few 
seconds  the  impossi- 
bility of  escape  seemed 
to  reach  the  animal's 
brain,  when  it  at  once 
turned  round  and 
opened  its  great  pink 
mouth  in  the  face  of 
the  advancing  foe,  at 
the  same  time  rapidly 
changing  colour,  be- 
coming almost  black. 
This  ruse  succeeded  , 

FIG.     15. — Common      Starfish      (Astenas 

every     time,    the     dog  rubens)   regenerating    lost    parts.      It 

tnrnincr    off    af     OTIPP  '  shows  at  the  top  two  arms  which  are 

irmng  ott  at    once  .  just  beginning  to  be  regrown.    The 

Mr.     Crossland     points  largest    of    the    five    arms    has   been 

.          .                      ,  previously    regrown    double.       (After 

out    that    m    natural  Mclntosh.) 


40  THE  WONDER  OF  LIFE 

leafy  conditions  the  startling  effect  would  be  enhanced — 
a  sudden  throwing  off  of  the  mantle  of  invisibility  and  the 
exposure  of  a  conspicuous  black  body  with  a  large  red 
mouth. 

There  is  no  end  to  these  effective  adaptations,  and  all 
that  we  are  concerned  with  here  is  the  illustration  of  a  very 
remarkable  aspect  of  the  drama  of  life.  We  know  how 
cuttlefishes  throw  dust  (or  ink)  in  the  eyes  of  their  pursuers  ; 
how  the  skunks  repel  by  their  loathsome  stench  ;  how  the 
starfish  escapes  by  surrendering  an  arm,  the  crab  by  giving 
up  its  claw,  and  the  lizard  by  parting  with  its  tail ;  how 
the  puss-moth  caterpillar  puts  on  '  a  terrifying  attitude  ', 
and  the  cat  effectively  '  bluffs '  the  dog.  Of  a  truth  it 
may  be  said  of  Life  that  it  has  sought  out  many  inventions. 

Intricate  Situations. — Other  illustrations  of  the  dra- 
matic element  in  Animate  Nature  may  be  found  in  the 
frequent  occurrence  of  intricate  situations.  Many  of 
these  arise  from  the  complex  inter-relations  which  have 
in  the  course  of  time  been  established.  As  we  propose 
to  give  many  examples  of  these  inter-relations  in  a  subse- 
quent chapter,  it  may  suffice  here  to  recall  the  general 
Darwinian  conception  of  the  '  Web  of  Life  ', — that  Nature 
is  a  vibrating  system  most  surely  and  subtly  inter- 
connected. No  organism  lives  or  dies  quite  to  itself, 
each  being  in  some  way  correlated  with  some  other. 

In  Illustration  :  Cuckoo- Spit. — The  impression  of  the 
subtlety  and  intricacy  of  life,  which  we  wish  to  convey, 
might  be  illustrated  by  taking  rare  and  quaint  instances, 
but  the  commonest  things,  curiously  enough,  are  always 
the  most  striking.  In  early  summer  in  temperate  countries 
nothing  is  commoner  on  the  herbage  than  the  splashes  of 
white  froth  which  are  often  called  '  cuckoo-spit '.  The 


THE  DRAMA  OF  LIFE  41 

old  idea  was  that  the  mother- cuckoo  spat  them  out  as  she 
flew  around  looking  for  a  suitable  nest  in  which  to  place 
her  egg,  and  it  was  also  supposed  by  some  that  they  gave 
rise  spontaneously  to  singing  Cicadas.  They  have,  of 
course,  nothing  to  do  with  cuckoos,  but  they  have,  in  a 
sense,  something  to  do  with  cicadas,  for  they  are  produced 
by  the  larvae  of  insects,  e.g.  Aphrophom  spumaria,  which 
are  related  thereto.  They  are  popularly  known  as  frog- 
hoppers,  in  allusion  to  the  highly  developed  jumping 
powers  of  the  adults. 

The  eggs  are  laid  the  previous  autumn  by  the  mother 
'  froghopper  '  in  deep  crevices  in  the  bark  of  willow-bushes 
or  the  like ;  they  hatch  in  spring,  and  there  emerge  small 
squat  larvae  with  a  piercing  beak  and  firmly  gripping  legs. 
These  probe  the  leaves  and  stems  of  plants  and  suck  up  the 
sugary  sap,  much  as  their  relatives  the  green-flies  or  Aphides 
do.  And  just  as  '  honey- dew ',  as  it  is  called,  passes  out 
of  the  food-canal  of  the  green-flies  in  large  quantities  and 
smears  the  leaves  and  even  falls  like  drops  of  rain  to  the 
ground,  so  the  surplus  sap  passes  through  the  frog-hoppers 
and  forms  the  familiar  foam-like  '  spit '.  The  food  is  very 
abundant,  the  larva  grows  and  moults,  and  grows  and 
moults  again,  and  finally  passes  into  a  resting  or  pupa 
stage ;  its  wings  grow  and  other  changes  of  structure  are 
brought  about ;  it  leaves  the  froth  and  moults  for  the  last 
time  ;  it  becomes  a  full-grown  winged  insect,  and  there  is 
no  more  foam  to  be  seen  on  the  herbage.  All  the  frog- 
hoppers  have  grown  up. 

The  making  of  the  foam  which  envelops  and  conceals  the 
larval  frog-hopper  is  of  much  interest.  In  the  first  place, 
the  material  is  watery  sap,  slightly  changed  by  passing 
through  the  food-canal ;  it  is  exuded  at  the  hind  end  and 


42  THE  WONDER  OF  LIFE 

spreads  over  the  body  and  limbs.  In  the  second  place, 
there  is  an  external  air-canal,  a  sort  of  closeable  gutter  on 
the  under  surface  of  the  body  posteriorly,  in  which  the 
insect  collects  air  from  the  outer  world  and  from  which  it 
can  expel  it  into  the  surrounding  clear  fluid.  If  we  watch 
carefully  we  can  see  the  larva  raising  the  end  of  its  body 
to  the  surface  of  the  froth  and  allowing  the  air- canal  to  fill ; 
thereafter  the  canal  is  used  like  a  pair  of  bellows  and  air 
is  blown  into  the  fluid.  Some  of  the  air  is  of  course  utilized 
for  the  insect's  breathing.  In  the  third  place,  there  are 
minute  wax  glands  on  two  of  the  segments  of  the  hind 
part  of  the  body,  which  produce  small  quantities  of  wax. 
This  is  acted  on  by  a  ferment  in  the  exuded  fluid  and  a 
sort  of  soap  is  formed  !  If  it  were  not  for  this  soap-pro- 
duction the  bubbles  would  not  last  so  long  as  they  do. 

It  is  a  very  remarkable  device,  living  under  water  and 
yet  in  the  open  air,  conspicuous  and  yet  concealed,  in  the 
sunshine  and  yet  cool !  Though  the  frog-hoppers  are  some- 
times picked  out  from  their  frothy  shelter  by  audacious 
wasps  and  the  like,  there  can  be  no  doubt  that  they  are 
saved  from  many  enemies  and  many  risks  by  having 
acquired  the  art  of  blowing  soap-bubbles.  For  that  is 
precisely  what  happens. 

The  Case  of  Horned  Lizards. — Among  terrestrial 
animals,  the  lizards  stand  easily  first  in  the  exhibition  of 
quaint  and  bizarre  forms.  It  seems  as  if  Nature  had,  so  to 
speak,  let  herself  go  among  lizards  in  quips  and  cranks. 
How  like  a  joke  the  chameleon  and  many  another  quaint 
lizard  seems  till  we  see  them  in  their  appropriate  environ- 
ment and  at  their  daily  work.  We  are  thinking  of  forms 
like  the  little  dragon  (Draco  volans),  with  its  skin  webbed 
between  enormously  extended  ribs ;  or  the  Australian 


THE  DRAMA  OF   LIFE  43 

moloch,  with  its  curiously  hygroscopic  skin,  pimpled  all 
over  with  sharp  tubercles ;  or  the  frilled  lizard  which 
Saville  Kent  describes,  that  runs  totteringly  about  on  its 
hind  legs  like  a  baby  just  before  it  falls  ;  or  the  basilisk, 
with  erectile  crests  on  its  back ;  or  our  own  British  slow- 


Fia.  16. — Frilled  Lizard  (Chlamydosaurus)  running  like  a  biped,  with  its 
collar  folded  round  its  head.     (After  Saville  Kent.) 


worm,  which  has  put  on  the  guise  of  a  snake,  and  is  famous 
for  the  ease  with  which  it  can  surrender  its  tail  to  save  its 
life. 

In  the  show  of  quaint  lizards  the  chameleon  must  always 
be  awarded  the  first  prize ;  but  many  will  agree  with  us 
in  thinking  that  the  horned  lizards  of  Mexico,  California, 
and  Nevada  come  a  good  second.  They  have  been  known 
for  a  long  time,  but  they  have  been  made  the  subject  of 
a  recent  monograph  by  Mr.  Harold  C.  Bryant,  of  the 
University  of  California.  To  this  fine  piece  of  work — one 
envies  the  author  his  subject — we  are  indebted  for  some 


44 


THE  WONDER  OF  LIFE 


FIG.  17. — Frilled  Lizard  of  Australia  (Chlamydosaurus  kingi)  with  a  great 
erectile  frill  on  the  neck,  folded  when  the  creature  runs,  expanded 
when  it  stands  at  bay.  The  animal  grows  to  nearly  3  feet.  (After 
Saville  Kent.) 

new  and  interesting  material.  The  creatures  in  question 
are  often  spoken  of  as  '  horned  toads  ',  the  false  classifica- 
tion being  probably  suggested  by  their  squat  shape,  their 
sluggish  ways,  and  their  habit  of  catching  insects  on  a 
sticky  tongue.  True  lizards  they  undoubtedly  are,  and 


THE  DRAMA  OF  LIFE  45 

among  the  Iguanids ;  but  they  differ  from  all  other  mem- 
bers of  the  order  in  their  flat  bodies  covered  with  keeled, 
spiny  scales,  and  in  the  circlet  of  horns  upon  the  head. 
There  are  eighteen  different  species  belonging  to  the  genus 
Phrynosoma,  and  there  is  one  other  known,  a  unique  creature 
from  the  deserts  of  the  Gila  and  Colorado  Rivers,  which 
requires  a  genus  (Anota)  all  to  itself,  and  has  the  honour, 
indeed,  of  differing  from  every  other  living  lacertilian  in  the 
closing  up  of  a  small  gap  on  the  roof  of  the  skull  known 
as  the  supratemporal  foramen.  One  needs,  however,  to 
know  a  good  deal  about  skulls  before  one  can  appreciate 
the  importance  of  this  unique  feature. 

What  is  the  significance  of  the  Phrynosome's  peculiarities? 
In  the  first  place,  what  is  the  meaning  of  that  circlet 
of  sharp  horns  on  the  head,  which  recall  (as  if  in  miniature) 
the  projecting  horns  of  some  of  the  extinct  Dinosaurs  ? 
The  curious  shape  of  head  that  results  reminds  one  also  of 
the  quaint  fruits  of  the  water-chestnut  which  the  peasants 
round  Florence  string  into  most  decorative  rosaries.  But 
what  are  the  horns  for  ?  They  serve  to  ward  off  blows 
and  bites,  for  the  creature  lowers  its  head  and  raises  the 
scales  of  its  back  when  it  is  on  the  defensive,  and  we  can 
well  believe  that  if  an  enemy  bit  the  head  of  a  Phrynosome 
once,  it  would  never  do  so  again.  The  Indians  say  that 
if  a  snake  swallows  one  whole,  the  indomitable  lizard 
proceeds  to  work  its  way  by  a  short  cut  from  the  stomach 
outwards — which  for  the  aggressor  must  be  an  extremely 
disagreeable  process,  bringing  repentance  to  the  snake. 
Mr.  Bryant  says  that  there  is  some  foundation  for  this 
story,  and  it  has  its  analogues  at  any  rate  in  records  of 
box-fishes  biting  their  way  out  of  sharks. 

A  second  distinctive  feature  in  the  homed  lizards  is  their 


46  THE   WONDER  OF  LIFE 

power  of  adaptive  colour- change.  They  have  the  secret  of 
the  Gyges  ring,  and  putting  on  the  garment  of  invisibility 
is  for  them  as  easy  as  winking.  '  Wherever  its  home  ',  says 
the  monographer,  *  the  horned  lizard  resembles  the  colour 
of  the  substratum  so  closely  that  it  is  practically  invisible 
except  when  in  motion.  Specimens  from  the  white  sand 
of  the  desert  are  very  light  in  colour,  those  from  the 
black  lava  belt  are  almost  black,  whereas  those  from  the 
vari- coloured  mountain  districts  show  red  and  even 
bluish  markings.  How  quickly  a  change  of  environment 
would  bring  about  a  change  in  colour  is  not  definitely 
known,  although  Coues  states  that  the  change  takes  place 
in  from  twenty-four  to  forty- eight  hours '. 

Given  horns  and  scales  and  the  mantle  of  invisibility, 
the  horned  lizards  are  safe,  and  we  are  not  surprised  to  learn 
that  most  of  the  species  are  represented  by  large  numbers 
of  individuals.  We  can  understand  now  why  they  have 
such  a  wide  geographical  range  from  Canada  to  southern 
Mexico,  and  from  the  Mississippi  to  the  Pacific  coast ; 
why  they  rarely  bite  ;  why  they  can  afford  to  take  things 
easily,  basking  in  the  sun  and  moving  with  leisurely  deliber- 
ation. When  an  enemy  comes  they  '  play  'possum ' ; 
when  they  are  thoroughly  scared  they  seek  refuge  in  a  bush 
or  burrow  in  the  sand. 

Even  in  their  burrowing  they  are  unlike  most  other 
creatures,  for  they  work  their  way  beneath  the  ground 
head-foremost.  As  Mr.  Bryant  says,  '  The  chisel-shaped 
head  is  the  principal  tool,  the  legs  being  used  almost 
solely  for  forcing  the  head  forward.  A  wriggling  motion 
of  the  head  and  body  serves  to  drive  the  head  beneath  the 
sand  and  soon  covers  the  body  completely  with  earth. 
A  little  shake  of  the  tail  flings  the  dirt  over  that  appendage, 


THE  DRAMA  OF  LIFE  47 

and  the  lizard  becomes  entirely  hidden.  The  nostrils  are 
kept  either  at  the  surface  of  the  ground  or  near  enough  to 
the  surface  so  that  breathing  is  possible  '.  Sometimes  the 
spines  are  left  protruding  above  the  ground  like  dry  thorns. 

Stranger  even  than  the  circlet  of  horns  and  the  wonder- 
fully perfect  power  of  colour-change  is  the  habit  of  '  shed- 
ding tears  of  blood '.  It  was  for  this  that  the  Mexicans 
called  the  Phrynosome  the  '  sacred  toad ' ;  it  is  to  this 
that  the  boys  of  San  Diego  refer  when  they  say  they  saw 
the  creature  '  spit  blood  '.  As  there  are  the  best  of  physio  - 
logical  reasons  why  it  can  neither  '  weep  blood '  nor  '  spit 
blood ',  what  is  it  that  happens  ?  The  eyes  are  tightly 
shut,  the  eyelids  swell  to  twice  or  thrice  their  normal  size, 
and  a  fine  jet  of  blood  shoots  out  for  several  inches  from 
beneath  the  upper  eyelid.  The  whole  phenomenon  is 
startling  and  quite  worthy  of  the  strange  creature.  Some 
say  that  the  haemorrhage  is  associated  with  the  excite- 
ment of  the  breeding  season,  but  this  lacks  proof.  So  far 
as  experiments  go,  they  seem  to  indicate  that  the  rush  of 
blood  is  associated  with  shock  and  fright.  The  eyelids  are 
rich  in  blood-vessels,  and  what  happens  is  first  a  congestion 
and  then  probably  the  rupture  of  a  blood-vessel.  It  may 
be  compared  to  bleeding  at  the  nose,  but  the  point  is  that 
it  has  been  regularized.  One  physiologist  has  suggested 
that  the  flooding  of  the  head  sinuses,  the  elevation  of  the 
blood  pressure,  and  the  jet  of  blood,  while  associated  with 
panic  and  excitement,  may  also  have  a  frightening  effect 
deterrent  to  enemies. 

The  horned  lizards  are  for  the  most  part  insectivorous, 
catching  living  ants,  beetles,  and  flies  on  the  end  of  the 
viscid  tongue.  '  Why  the  animal  is  never  bothered  by 
being  stung  internally  by  the  ants  it  swallows  alive  seems 


48  THE  WONDER  OF  LIFE 

hard  to  explain.'  It  is  sensitive  enough  externally ;  can 
it  be  that  it  is  immune  internally  ?  When  insects  become 
scarce,  and  the  cold  weather  sets  in,  the  horned  lizards 
burrow  into  the  ground  and  pass  into  the  coma  of  hiberna- 
tion. Dr.  Gadow  makes  the  interesting  note  that  if  cap- 
tive specimens  are  not  allowed  to  hibernate,  '  they  will  keep 
on  feeding  through  the  winter,  but  in  that  case  are  sure  to 
die  in  the  following  spring '. 

We  may  leave  the  horned  lizards  in  their  winter  sleep, 
though  without  nearly  exhausting  their  peculiarities.  One 
more  may  be  mentioned,  which,  like  the  haemorrhage,  well 
deserves  further  study.  Mr.  Bryant  has  found  that  they 
are  very  amenable  to  what  looks  like  hypnosis.  When  a 
specimen  is  rubbed  on  the  top  of  the  head  and  between  the 
eyes,  it  turns  its  head  down,  closes  its  eyes,  and  passes 
into  a  stupor,  in  which  it  may  remain  for  five  or  ten  minutes. 
But  the  observer  was  not  quite  sure  whether  what  happened 
was  a  faint,  or  a  feint,  or  neither.  It  presents  one  of  those 
unsolved  problems  with  which  every  study  in  Natural 
History  should  begin  and  also  end. 

Love -Scenes. — The  interest  of  many  a  human  drama 
is  in  its  love-affairs — two  men  and  a  maid,  two  maids 
with  their  hearts  set  on  one  man — such  are  the  apparently 
simple  data  from  which  a  plot  is  evolved.  And  it  is  so 
among  animals  also.  We  need  not  quibble  about  words ; 
the  love  of  the  Argus  pheasant  showing  off  his  hundred 
eyes  before  his  desired  mate  is  doubtless  very  different 
from  the  love  of  the  stickleback  coaxing  and  driving  his 
bride  to  the  nest  among  the  weeds,  and  both  are  very 
different  from  our  loves,  but  there  is  undoubtedly  a  com- 
mon element.  We  must  avoid  the  amiable  error  of 
generosity — reading  the  man  into  the  beast — but  we  must 


THE  DRAMA  OF  LIFE  49 

avoid  the  opposite  error  of  excessive  stinginess  which 
reduces  the  animal  to  the  level  of  an  automatic  machine. 
The  true  view  is  between  these  extremes. 

Among  the  loves  of  animals,  we  may  find  what  is  common- 
place (when  there  is  not  the  slightest  hint  of  preferential 
mating),  but  we  also  find  the  extraordinary,  as  when  a  she- 
spider  puts  an  abrupt  full  stop  to  a  courtship  by  devouring 
her  suitor.  We  find  what  provokes  us  to  mirth,  as  when  a 
male  spider  waltzes  over  a  hundred  times  around  his 
desired  mate  at  a  respectful  radius ;  we  find  also  what 
seems  pathetic,  as  in  the  familiar  nuptial  flights  of  the 
ants,  where  the  apparent  waste  of  masculinity  is  so  enor- 
mous— worse  than  the  worst  of  wars. 

Let  us  travel  to  the  meadows  around  Bologna.  It  is 
late  on  a  summer  night,  when  the  darkness  is  short.  It  is 
very  quiet,  for  even  the  frogs  have  ceased  for  weeks  to  utter 
their  cheerful  brek-a-brek  whose  interrogativeness  expresses 
the  essence  of  conversation.  There  seem  to  be  living  sparks 
in  the  air  and  lesser  lights  among  the  grass.  It  is  the 
courtship  of  Luciola — the  Italian  fire-fly.  The  lady- 
Luciolas  are  sedentary ;  the  males  fly  about.  When  a 
female  catches  sight  of  the  flashes  of  an  approaching  male 
she  allows  her  splendour  to  shine  forth.  He  sees  the 
signal,  and  is  forthwith  beside  her,  circling  round  like  a 
dancing  elf.  But  one  suitor  is  not  enough,  and  the  lady- 
Luciola  soon  attracts  a  levee.  In  apparently  courteous 
rivalry  her  devotees  form  a  respectful  circle,  flashes  of  light 
come  and  go,  and  eventually  in  the  dead  of  night  the 
coquette's  choice  is  made.  In  the  two  sexes,  Prof.  Emery 
says,  the  colour  and  intensity  of  the  light  is  much  the  same, 
but  the  luminous  rhythm  of  the  male  is  more  rapid,  with 
briefer  flashes  ;  while  that  of  the  female  is  more  prolonged, 


50  THE  WONDER  OF  LIFE 

with  longer  intervals,  and  more  tremulous — suggestive 
indeed  of  the  contrasts  among  higher  non-luminous 
creatures.  The  picture  is  dramatic. 

Family  Life. — Why  do  the  people  thus  strive  and  cry  ? 
the  poet  asked,  and  the  wise  answer  came  :  '  They  will 
have  food,  and  they  will  have  children,  and  they  will 
bring  up  the  children  as  well  as  they  can.'  This  is  true 
for  us ;  it  is  also  true  for  animals,  and  there  often  is  a 
dramatic  element  in  nurture.  The  mind  fills  with  all  sorts 
of  illustrations  of  parental  care — the  kangaroo  placing  her 
newborn  babe — unable  even  to  suck — into  her  skin-pocket ; 
the  mother  crocodile  who  digs  up  the  buried  eggs  when  she 
hears  the  restless  young  piping  their  slender  signal  from 
within  the  egg — it  would  not  be  well  to  be  born  buried 
alive ;  the  father  frog  (Rhinoderma)  who  carries  the  eggs 
and  even  the  froglets  in  his  croaking  sacs,  yet  does  not 
swallow  them — and  so  on  ;  down  and  down — to  the  skate  - 
sucker  that  mounts  guard  for  months  over  its  egg-clusters 
laid  in  a  shell,  or  the  little  brook-leech  that  bears  about  its 
young  hanging  on  to  the  body.  But  there  are  instances  in 
which  the  dramatic  element  is  more  apparent  than  in  these. 

Let  us  spread  the  wings  of  our  imagination  again  and 
travel  to  some  warmer  clime — Africa,  Australia,  but  pre- 
ferably India — to  some  place  where  hornbills  are  at  home. 
These  birds,  well  known  for  the  helmet  on  their  head,  are 
tree-lovers,  except  when  feeding ;  though  their  bones  are 
more  pneumatic  than  those  of  most  birds,  they  fly  heavily 
and  slowly, — most  of  them  with  a  sound  like  that  of  a 
steam-engine  in  the  distance ;  their  characteristic  note  is 
between  the  bray  of  an  ass  and  the  shriek  of  a  railway 
engine ;  they  are  somewhat  indiscriminating  feeders, — 
in  many  ways,  in  short,  not  very  attractive.  But  in 


THE  DRAMA  OF    LIFE  51 

one  respect  their  behaviour  excites  our  admiration — the 
behaviour  of  the  male  bird  to  his  mate  and  offspring. 

When  nesting-time  comes,  a  hole  in  a  tree  is  found,  and 
the  wife  goes  in  and  shuts  the  door.  From  material  which 
she  has  gathered  or  which  her  husband  brings  she  walls 
herself  in — literally  '  barring  the  door  weel '.  Only  a  small 
opening — like  the  grille  in  the  convent  door — is  left ; 
perhaps  it  helps  to  keep  snakes  and  other  enemies  out. 
Through  the  window,  however,  the  father  feeds  her,  knock- 
ing with  his  bill  if  she  is  not  on  the  outlook ;  as  he  clings 
to  the  bark  he  is  (if  nature  be  not  a  mirage)  obviously 
anxious  about  his  charge  ;  she  sits  safe  minding  her  own 
business,  he  works  hard  bringing  succulent  fruit,  or  tender 
mouse,  or  juicy  frog  ;  curiously  enough  he  sometimes  casts 
up  the  lining  of  his  gizzard  with  all  its  contents  enclosed 
— a  strange  votive  offering  on  the  family  altar.  We  are 
not  surprised  to  learn  that  by  the  time  the  young  bird 
is  ready  to  emerge  the  devoted  father  and  husband  '  is 
worn  to  a  skeleton '.  The  story  is  dramatic. 

Complications. — There  is  a  novel  by  Turgemef  called 
A  Friend  of  the  Family  in  which  are  depicted  some  of  the 
disadvantages  attendant  on  the  guest  out-staying  his 
welcome.  But  there  are  far  more  complicated  problems 
involved  in  the  habit  many  ants  have  of  being  hosts  to 
beetles.  To  make  the  matter  clear,  a  brief  introductory 
statement  must  be  made.  Just  as  we  have  or  may  have 
in  or  about  our  houses  five  sets  of  living  creatures — parasites 
like  the  homceopathist's  leech  whose  name  of  flea  it  is 
impolite  to  mention,  really  inimical  intruders  like  rats, 
more  or  less  indifferent  fellow-inmates  like  the  death- 
watch,  useful  domestic  animals  like  the  cow,  and  pets  like 
the  cat,  so  ants  may  have  in  their  nests  parasites  in  the 


52  THE  WONDER  OF  LIFE 

form  of  mites,  unfriendly  intruders,  indifferent  fellow- 
tenants,  occasional  '  cows '  (as  Linnaeus  called  the 
Aphides),  and  pets.  These  pets  are  usually  Staphylinid 
beetles  belonging  to  the  family  well-represented  in 
Britain  by  the  devil's  coach-horse  (Ocypus  olens}.  Some 
of  the  Staphylinids  are  downright  robbers  and  others  are 
merely  tolerated  by  the  ants,  but  there  is  a  third  set 
(represented  by  the  genera  Atemeles  and  Lomechusa)  to 
which  the  name  of  pet  may  be  applied.  These  beetles 
are  never  found  outside  or  at  any  rate  very  far  from  the 
ants'  nests ;  they  have  patches  of  yellow  hairs  which 
seem  to  secrete  some  substance  which  the  ants  like  to  lick  ; 
they  seem  to  be  on  very  friendly  relations  with  the  ants,  for 
they  stroke  them  and  get  drops  of  honey  from  their  mouths, 
and  they  will  in  turn  disgorge  some  of  their  repast  for  the 
benefit  of  a  hungry  host.  On  the  other  hand,  these  friends 
of  the  family  are  not  so  innocent  as  they  appear,  for  while 
with  bended  knee  they  will  solicit  a  bonne  bouche  from 
their  hosts,  and  while  they  like  to  sit  among  a  crowd  of 
ants  as  if  exchanging  the  compliments  of  the  season,  they 
are  on  the  sly  eating  up  a  good  many  of  the  ants'  children 
— and  that  when  their  own  are  receiving  food  from  the  ants. 
And  now  we  come  to  our  precise  point.  Looking  down — 
through  Father  Wasmann's  eyes — on  this  quaint  association 
of  hosts  and  guests,  we  feel  safe  in  saying  that  the  presence 
of  the  beetles  adds  to  the  ants'  sum-total  of  happiness,  and 
yet  we  cannot  avoid  doubting  whether  the  amiable  hospital- 
ity of  the  '  little  people,  exceeding  wise '  has  not  in  it  elements 
of  danger.  What  if  the  guests  became  too  numerous  ? 

As  a  fine  example  of  wheels  within  wheels,  let  us  face 
this  question  and  inquire  what  actually  happens.  The 
beetles  are  not  unlike  ants  in  their  ways,  and  the  larvae  of 


THE  DRAMA  OF  LIFE  53 

Lomechusa,  as  described  by  Wasmann,  are  very  like  ant 
larvae.  At  any  rate,  the  ants  make  little  distinction 
between  the  ant- larvae  and  those  of  their  guests  ;  they  treat 
them  both  alike.  Now  it  is  the  habit  of  the  worker-ants 
to  dig  up  the  ant-larvae  and  to  clean  them  during  the  pupal 
metamorphosis  ;  and  they  do  this  likewise  for  their  guests' 
larvae.  But  while  it  is  a  good  procedure  for  the  ant- 
larvae,  it  is  disastrous  to  the  beetle- larvae ;  the  great 
majority  perish  under  the  treatment  and  perhaps  only 
those  which  have  been  overlooked  survive.  Two  naturalists 
at  least  have  referred  to  this  as  an  unfortunate  circum- 
stance, as  an  illustration  of  the  well-known  fact  that  '  the 
best-laid  plans  of  mice  and  men  gang  aft  agley ',  but  in 
reality  the  apparent  failure  is  an  unconscious  success  ; 
the  result  of  the  wheels- within- wheels  complication  is  that 
the  friends  of  the  family  do  not  become  too  embarrass- 
ingly numerous. 

Karl  Jordan  has  made  an  interesting  study  of  the  glands 
of  Lomechusa  and  Atemeles  and  other  related  beetles  which 
live  as  guests  in  ants'  nests.  Numerous  unicellular  glands 
on  the  sides  of  the  abdomen  produce  the  secretion  that  the 
ants  lick  with  evident  gusto.  But  there  are  also  numerous 
offensive  glands,  common  to  other  beetles  of  the  same 
sub-family  Aleocharinae  which  are  not  myrmecophilous. 
The  secretion  of  these  offensive  glands  has  an  odour  like 
that  of  amyl-acetate  or  methyl- heptenon,  and  it  has, 
like  these  substances,  a  stupefying  effect  on  the  ants.  It 
is  used  against  stranger  ants  or  against  the  hosts  them- 
selves when  they  are  troublesome.  The  possession  of  the 
offensive  glands  gives  the  beetles  a  certain  standing,  so  to 
speak,  but  it  is  on  the  possession  of  the  palatable  secretion 
that  the  myrmecophilous  partnership  depends. 


CHAPTER   11 

THE  HAUNTS  OF  LIFE 

(THE  EXPLOITATION  OF  THE  EARTH) 

'Sbe  bas  oivioeo  berself  tbat  sbe  mas  be  ber  own  oelfgbt. 
Sbe  causes  an  enoless  succession  of  new  capacities  for 
enjoyment  to  spring  up,  tbat  ber  insatiable  sgrnpatbg  mag 
be  assuageD.  .  .  .' 

'Sbe  tosses  ber  creatures  out  of  notbfngness,  ano  tells 
tbem  not  wbence  tbeg  came,  nor  wbitber  tbeg  go.  5t  is 
tbeir  business  to  run,  sbe  fcnows  tbe  roao.  .  .  .' 

— Ooethe's  Aphorisms,  translated  by  Huxley. 

The  Shore  Fauna — The  Pelagic  Fauna — The  Abyssal  Fauna — 
The  Freshwater  Fauna — The  Terrestrial  Fauna — The  Aerial 
Fauna. 

THERE  are  six  great  haunts  of  life  :  the  shore  of 
the  sea,  the  open  sea,  the  deep  sea,  the  freshwater, 
the  dry  land,  and  the  air.  And  these  have  their  distinctive 
tenants.  For  while  some  types  may  be  represented  by 
very  similar  forms  in  more  than  one  haunt,  and  while  some 
animals  pass  from  one  haunt  to  another,  yet  on  the  whole 
there  is  distinctiveness  in  the  faunas  of  the  various  regions. 
So  we  may  speak  of  littoral,  pelagic,  abyssal,  freshwater, 
terrestrial,  and  aerial  faunas.  Besides  the  great  haunts 
there  are  minor  haunts  of  much  interest — such  as  caves, 
and  brackish  water,  and  underneath  the  ground.  It  must 
be  granted,  too,  that  parasitic  animals  have  explored  and 
54 


THE   HAUNTS   OF  LIFE  55 

exploited  a  great  variety  of  haunts  in  or  on  other  creatures. 
In  strictness,  as  we  shall  recognize  later  on,  the  freshwater 
haunt  should  be  subdivided  into  several  distinct  haunts. 

I.    THE  SHORE  FAUNA 

We  must  think  of  the  shore-area  as  much  more  than 
that  stretch  of  sand  and  gravel  and  rock-pool  and  mud 
which  many  of  us  know  so  well — the  happy  hunting-ground 
of  child  and  naturalist  alike.  The  shore-area  is  much 
more  than  the  stretch  between  tide-marks.  It  includes 
the  whole  of  the  shallow  shelf  around  continents  and  con- 
tinental islands,  down  to  a  depth  of,  say,  100  fathoms.  It 
is  the  area  where  seaweeds  grow.  Geographers  tell  us 
that,  without  including  the  imperfectly  known  polar  areas, 
the  shore-area  stretches  for  over  150,000  miles  and  has  a 
superficial  extent  of  perhaps  nine  million  square  miles. 
It  is  therefore  an  immense  area,  though  it  only  occupies 
between  6  and  7  per  cent,  of  the  entire  sea-surface.  It 
makes  up  for  its  relative  smallness  by  the  density  and 
variety  of  its  population. 

What  strikes  us  first  about  the  littoral  area  is  that  it  is 
the  meeting-place  of  the  terrestrial,  the  freshwater,  the 
pelagic,  and  the  abyssal  faunas.  Over  the  marshy  ground 
overflowed  at  high  tides,  or  over  the  firm-turfed  links,  or 
abruptly  up  the  cliffs,  or  tediously  over  the  seemingly 
interminable  sand-dunes,  we  pass  from  the  littoral  to  the 
terrestrial.  Up  the  long  estuary  there  is  often  a  gradual 
passage  from  salt  water  to  fresh,  and  we  notice  some  ani- 
mals like  flounders  that  don't  seem  to  care  which  they  live 
in.  If  we  take  a  boat  and  sail  out,  or  if  we  swim  out  in 
some  places,  we  pass  from  the  littoral  to  the  pelagic  area. 
If,  on  the  other  hand,  we  could  walk  down  the  gently 


56  THE  WONDER  OF  LIFE 

sloping  shelf  that  often  occurs,  we  should  find  the  light 
becoming  gradually  fainter  and  the  seaweeds  becoming 
gradually  scarcer,  and  if  we  could  continue  to  a  depth  of 
about  100  fathoms,  we  should  come  to  the  '  mud-line  ' 
where  wave-action  ceases  and  the  mud  sinks  quietly  to 
rest.  This  is  near  the  edge  of  the  continental  shelf,  and 
beyond  this  is  the  steep  slope  leading  down  to  the  deep 
sea. 

The  shore-area  has  been  divided  by  Forbes  and  others 
into  zones  :  (a)  the  strictly  Littoral  or  tidal  zone,  between 
the  tide-marks,  with  limpets  and  acorn-shells,  periwinkles 
and  dog-whelks,  cockles  and  mussels,  sea-anemones  and 
crumb-of-bread  sponge ;  (6)  the  Laminarian  zone,  where 
the  long  pennon-like  brown  seaweeds  grow  in  profusion 
with  sea-urchins  and  starfishes  and  nudibranchs  ;  and  (c) 
the  Coralline  zone,  with  abundance  of  calcareous  Algse,  and 
such  animals  as  '  buckies '  and  '  sea- mice'.  But  shores 
differ  so  enormously  that  these  zones  are  not  of  general 
occurrence  ;  a  great  deal  depends  on  the  gradient,  for  the 
shelf  may  extend  out  for  many  miles,  or  there  may  be  deep 
water  up  to  the  sides  of  the  cliffs  and  no  shore  at  all,  as  in 
the  Scandinavian  fjords.  A  noteworthy  point  that  can  be 
readily  verified  concerns  the  seaweeds.  The  dominant 
colour  changes  as  we  proceed  outwards.  Most  of  the 
green  Alga3,  such  as  the  sea-lettuce  (Ulva  lactuca),  are  in 
the  shallowest  water ;  the  brown  ones,  such  as  the  huge 
Laminarians,  are  most  predominant  further  out ;  the 
red  Algse,  such  as  Delesseria  sanguined,  are  especially  char- 
acteristic of  the  lowest  zone  of  seaweeds.  In  the  brown 
forms  the  chlorophyll  is  masked  with  a  brown  pigment 
(phycophaein),  in  the  red  forms  with  a  red  pigment  (phyco- 
erythrin),  and  the  point  of  greatest  interest  is  simply  that 


THE   HAUNTS  OF  LIFE  57 

the  red  seaweeds  are  able  to  continue  the  work  of  assimila- 
tion in  relatively  faint  light,  though  they  do  not  form  the 
ordinary  kind  of  starch.  It  may  be  noted  in  passing  that 
the  pelagic  Sargasso  weed  consists  of  pieces  of  littoral  sea- 
weeds (e.g.  Sargassum)  which  have  been  torn  by  storms 
from  the  shore  and  floated  outwards. 

It  is  usually  believed  that  the  green  Algse  came  first 
historically,  but  it  is  interesting  to  notice  Brunnthaler's 
heresy  that  the  red  ones  are  most  primitive.  His  idea  is 
that  the  red  Algse  were  physiologically  best  suited  for  the 
dim  light  of  very  ancient  days  when  the  Earth  was  enveloped 
in  a  dense  cloud  canopy,  just  as  they  are  nowadays  best 
suited  for  the  deeper  waters  of  the  littoral  area.  Those 
with  brown  pigment  came  next  and  they  were  well  suited 
to  absorb  rays  from  a  somewhat  lighter  but  still  very  misty 
atmosphere.  The  green  Algae  came  last  in  the  series,  when 
our  present-day  conditions  were  established.  They  proved 
very  successful  and  spread  from  the  sea  to  the  estuaries  and 
thence  into  the  freshwaters. 

Physical  Conditions. — The  character  of  the  shore - 
fauna  depends  in  part  on  the  chemical  composition  of  the 
water,  which  shows  considerable  diversity.  This  depends 
on  the  nature  of  the  rocks  and  sea-bottom,  on  what  the 
rivers  bring  down,  and  on  what  the  currents  sweep  along. 
The  nature  of  the  rocks,  whether  volcanic  or  calcareous, 
granitic  or  sandstone,  and  so  on,  is  also  of  much  importance , 
determining,  for  instance,  the  nature  of  the  rock-pools 
and  the  opportunities  for  attachment.  On  the  nature  of 
the  rocks  and  sea-floor  the  vegetation  of  seaweeds  in  part 
depends,  and  the  '  flora '  reacts  on  the  fauna. 

It  is  part  of  the  definition  of  the  shore-area  that  it  is 
illumined  (hence  its  rich  vegetation),  but  it  is  subject  of 


58  THE  WONDER  OF  LIFE 

course  to  the  vicissitudes  of  day  and  night  (unknown  in 
the  Deep  Sea)  and  of  the  seasons  (there  is  eternal  winter 
in  the  Deep  Sea).  The  vicissitudes  of  temperature  are 
much  more  marked  than  in  the  Open  Sea.  With  its  tides 
and  storms  and  floods,  the  shore-area  is  on  the  whole  very 
difficult  and  '  trying  '.  Its  tenants  must  be  familiar  with 
what  has  been  called  '  the  discipline  of  dislodgment'. 
We  may  refer  to  the  wreckage  of  life  seen  in  the  jetsam 
after  a  heavy  storm,  to  the  effects  of  a  very  hard  winter 
on  the  shore  population  the  following  summer,  and  to  the 
long-lasting  effects  of  the  last  eruption  of  Vesuvius  on  the 
fine  littoral  fauna  of  the  Bay  of  Naples. 

There  are,  it  is  true,  circumstances  in  which  the  life  of 
the  shore  is  sheltered  from  much  of  the  mercilessness  of 
the  physical  forces — we  are  thinking  of  the  deep  holes  whose 
sides  are  unsecured  except  by  the  severest  storms,  the 
sunny  shallows  on  the  inner  side  of  the  breakwater  formed 
by  a  barrier  coral-reef,  the  stretches  of  lagoon  protected 
by  a  mangrove  belt  a  mile  broad,  and  the  great  mud-line 
itself  where  wave-action  has  ceased.  These  are  instances 
of  conditions  where  delicate  organisms  may  live  a  sheltered 
life  even  within  the  littoral  area,  but  in  most  cases  the 
reverse  is  much  nearer  the  truth.  The  shore  is  a  hard 
school  where  lessons  are  driven  home  with  blows  and  where 
risks  are  continuous.  It  furnishes  many  illustrations  con- 
firming Tennyson's  conclusion  in  regard  to  one  aspect  of 
organic  Nature : 

That  life  is  not  as  idle  ore 
But  iron  dug  from  central  gloom 
And  heated  hot  with  burning  fears 
And  dipped  in  baths  of  hissing  tears 
And  battered  by  the  shocks  of  doom 
To  shape  and  use. 


FlG.  19.— Shore  scene  in  the  Mediterranean,  showing  sea-horses, 
the  red  coral  of  commerce  in  the  left  upper  corner,  a  branching 
red  Alcyonarian,  and  a  tube-inhabiting  worm. 


58  >W.    WONDER   OF 

coare*  fc*»  *£*  11  in 

fchf  I?-  nter 

u:  tl«-  are 

r-i-K-b  "-R;"  u«<:  <ty««  Sea.     With  ito  tides 

•»ivi  *4  -.'»'.<•«:•««»  is  on  the  whole  very 

it*  t«j>*&flt»  must  be  familiar  with 

*•««»'  ecu'  «i  scipline  of    dislodgment'. 

fTeckngy  tjf  life  seen  in  the  jetsam 
tb«  effects  of  a  very  hard  winter 
•  the  folJowiog  sximmer,  and  to  the 
the  last  eruption  of  Vesuvius  on  the 
the  Bay  of  Naples. 
.c,  oircum:-  ivhich  the  life  of 

sniwoiis  .nfi^nfiiwiibgM  sHl  ni  anaoa .  9ioH8— . °I  .Oil 
B  .ismoo  isqqu  rial  aHl  ni  soiammoD  lo  Ifiioo  bai  srli 
.nnow  sniiidBfini-sduJ  B  bns  .nBriBnoyoIA  bai 

side  of  th<  T  formed 

>  stretches  of  la;.  •  t«d 

broad,  and 
' n  has  ceased.     These  are  instances 

organisms  may 

:.  J8Hnm]  area,  but  in  most  cases  the 

truth.    The  shore  is  a  hard 

t  h  blows  and  where 

•  ;  .uy  illustrations  con- 

.rd  to  one  aspect  of 


'•>ars 


THE   HAUNTS   OF   LIFE  59 

A  Representative  Fauna. — The  shore-fauna  is  cer- 
tainly the  most  representative  of  all  faunas.  What  pic- 
tures rise  in  the  mind  !  Swiftly  moving  Infusorians  lash- 
ing their  way  through  the  water ;  Foraminifera  with 
beautiful  shells  of  lime  slowly  gliding  on  the  fronds  of  sea- 
weed ;  calcareous  sponges  like  little  vases  and  more  irregular 
flinty- and- horny  sponges,  sometimes  coating  the  rocks  like 
the  common  crumb-of-bread  sponge,  sometimes  growing 
in  beds  like  the  plants  they  were  once  supposed  to  be  ; 
hydroid  zoophytes  like  miniature  trees  on  rock  or  sea- 
weed ;  sea-anemones  and  corals  often  like  beds  of  flowers, 
living  an  easy-going  life,  waiting  for  food  to  drop  into 
their  mouths,  or  stinging  small  passers-by  ;  unsegmented 
worms  such  as  the  '  living  films  '  which  glide  on  the  sea- 
weeds or  stones  like  mysteriously  moving  leaves,  and  the 
Nemertines  or  ribbon-worms,  also  covered  with  cilia,  but 
provided  with  a  remarkable  protrusible  proboscis,  some- 
times ejected  so  violently  as  a  weapon  that  it  breaks  off 
altogether  and  wriggles  like  a  worm  itself  ;  the  higher 
ringed  worms  or  Annelids  in  extraordinary  numbers,  like 
Nereis,  Phyllodoce,  and  Aphrodite  itself,  so  beautiful  in 
themselves  and  in  their  names  that  we  can  understand 
the  enthusiasm  of  the  expert  who  is  said  to  have  named 
his  seven  daughters  after  seven  favourite  Polychaets  ;  the 
starfish  creeping  up  the  rocks  with  their  strange  hydraulic 
locomotor  system,  the  brittle- stars  using  their  lithe  arms 
like  gymnasts,  the  sea-urchins  tumbling  along  on  the  tips 
of  their  teeth,  and  the  sluggish  sea-cucumbers  plunging 
their  tentacles  into  the  mud  and  then  into  their  mouths  ; 
the  beautiful  colonies  of  '  Moss-animals '  or  Bryozoa, 
crusting  stone  and  weed  as  if  with  lace,  or  forming  leaf-like 
fronds  like  the  sea-mat  (Flustra),  which  was  one  of  the 


60  THE  WONDER  OF  LIFE 

first  animals  Charles  Darwin  worked  at,  or  growing  into 
calcareous  tufts  as  if  in  mimicry  of  corals  ;  myriads  of 
Crustaceans,  such  as  water-fleas,  acorn-shells,  beach- 
fleas,  sandhoppers,  no-body  crabs,  sea-slaters,  shrimps, 
hermit-crabs,  and  shore-crabs  proper  ;  strange  sea-spiders, 
neither  crustaceans  nor  spiders,  like  Pycnogonum  littorale, 
clambering  among  the  seaweeds  and  hydroids  ;  an  occa- 
sional insect  and  even  myriopod  about  high  tide  mark ; 
spiders  in  the  caves  and  among  the  dry  rocks  ;  bivalves 
innumerable,  such  as  cockles  and  mussels,  oysters  and 
razor-fish ;  herbivorous  gasteropods  like  periwinkles,  and 
voracious  carnivores  like  the  dog- whelks  and  buckies ; 
sedentary  limpets  with  a  slight  range  of  movement  and  a 
slight  memory  for  locality,  since  beyond  a  narrow  radius 
they  fail  to  find  their  way  home ;  an  occasional  cuttle- 
fish caught  in  a  shore-pool  and  many  more  further  out ; 
a  large  representation  of  ascidians  or  sea-squirts,  both 
simple  and  compound,  which  lie  at  the  base  of  the  Verte- 
brate series  ;  thelancelets  (Amphioxus)  buried  all  but  their 
mouth  in  the  fine  sand ;  true  shore-fishes  Like  sand-eels 
and  gunnels  and  shannies ;  an  occasional  reptile  like  the 
lizard  Amblyrhynchus  which  swims  out  among  the  rocks, 
or  a  poisonous  sea-snake,  or  a  turtle  coming  ashore  to  lay 
her  eggs ;  numerous  shore-birds  like  oyster- catcher  and 
rock  pipit,  gull  and  cormorant ;  and  an  occasional  mammal 
like  otter  and  seal — on  the  whole  a  more  representative 
fauna  than  in  any  other  life-area. 

We  must  not,  of  course,  include  among  the  shore  animals 
strayed  pelagic  forms,  such  as  jellyfishes,  which  are  often 
stranded  in  enormous  numbers.  Millions  of  inwafted 
"  Night-Light "  Infusorians,  Noctiluca,  sometimes  form  a 
reddish  brown  ridge  on  the  beach,  but  one  might  as  well 


THE   HAUNTS   OF   LIFE  61 

include  a  stranded  whale  in  the  littoral  fauna.  As  we  shall 
see  later  on,  many  of  the  distinctive  littoral  animals  pass 
through  a  pelagic  phase,  but  that  again  is  a  different  matter. 
Our  point  at  present  is  the  simple  one,  that  there  is  much 
in  the  jetsam  which  does  not  belong  to  the  shore. 

Keen  Struggle  for  Existence. — It  is  evident  that  the 
shore-area  must  be  characterized  by  a  keen  struggle  for 
existence.  In  the  open  sea  there  is  practically  no  limit  to 
the  floating  room  and  swimming  room,  but  the  shore  is 
narrow  and  crowded.  In  a  rock  pool  there  is  often  no 
vacant  niche.  There  is  competition  even  for  foothold.  It  is 
important  for  instance  that  the  limpet  which  makes  little 
journeys  in  search  of  seaweed  to  nibble  should  not  go  too 
far,  else  it  will  not  find  its  way  back,  and  will  have  lost 
the  spot  which  its  shell  has  grown  to  fit.  It  is  curious,  too, 
to  see  the  American  slipper-limpet — one  growing  on  the 
top  of  another  to  the  number  of  four  or  five — suggestive 
of  the  root-idea  of  a  sky-scraper. 

There  is  abundant  food  in  the  shore-area,  for  there  is 
a  great  crop  of  seaweeds  to  start  with,  but  there  is  nothing 
to  compare  with  the  pelagic  sea-meadows — an  inexhaustible 
supply  of  microscopic  Algae  extending  for  square  mile  after 
square  mile,  and  for  many  feet  in  depth.  Thus  on  the 
shore  there  is  much  more  struggle  for  food — competition 
around  the  platter.  It  is  lessened  by  the  fact  that  there 
is  considerable  variety  in  the  dietary,  some  being  carnivor- 
ous, others  vegetarian,  others  feeding  on  microscopic  ani- 
mals, and  others  on  debris,  but  one  must  remember  that 
even  the  crumbs  of  organic  matter,  formed  on  the  shore  or 
brought  down  by  rivers,  are  always  being  swept  away  by 
the  undercurrent  to  greater  depths.  The  most  must  be 
made  of  them  before  they  are  lost. 


62  THE  WONDER  OF  LIFE 

We  often  see  '  nutritive  chains ' — the  worm  feeding  on 
debris,  the  crab  feeding  on  the  worm,  the  shore-fish  swallow- 
ing the  crab,  the  herring  gull  with  a  swoop  lifting  the  fish 
from  near  the  surface  of  the  water,  the  skua  gull  chivying 
the  herring  gull  and  forcing  it  to  relinquish  its  booty. 
There  are  hundreds  of  similar  concatenations. 

There  is  struggle  for  foothold,  struggle  for  food,  and 
struggle  against  dislodgment ;  and  it  takes  every  form 
from  a  literal  struggle  for  subsistence  to  a  competition 
for  luxuries,  from  a  life  and  death  combat  to  a  rivalry 
of  wits.  The  oyster-catcher  tries  to  knock  the  limpet  off 
the  rock  with  a  dexterous  stroke  of  its  strong  bill,  the  limpet 
tries  to  hold  fast ;  the  carnivorous  sea-slug — sometimes 
secreting  dilute  sulphuric  acid  from  its  mouth — tries  to 
bore  through  the  back  of  a  starfish  which  may  succeed  in 
dislodging  its  enemy  by  creeping  under  a  low  shelf  of  rock  ; 
the  hermit-crab  seizes  a  worm,  the  worm  breaks  into  two, 
and  the  hermit-crab  falls  in  among  the  tentacles  of  a  large 
sea-anemone.  In  a  thousand  forms  there  is  that  reacting 
against  difficulties  and  limitations  which  is  the  essence  of 
the  struggle  for  existence. 

In  illustration  of  weapons  in  more  detail,  let  us  take  the 
case  of  the  sea-urchin.  Among  the  large  spines  on  its 
test  there  are  minute  ones  (pedicellarise)  with  three  snap- 
ping blades.  They  suggest  three-bladed  shears  on  the  end  of 
a  long  flexible  stalk.  Some  of  them  help  to  grapple  food- 
particles,  some  keep  the  test  clean,  and  others,  as  Prouho 
and  von  Uexkiill  showed,  give  poisonous  bites.  On  the 
dorsal  surface  of  the  beautiful  golden-yellow  heart-urchin, 
Echinocardium  ftavescens,  there  are  many  of  these  poisonous 
'  gemmiform  pedicellariae '  which  have  been  observed  to 
work  very  effectively.  G-andolfi  Horny  old  put  a  small 


THE   HAUNTS   OF  LIFE  63 

Annelid  worm  on  the  back  of  the  heart-urchin  and  watched 
the  spines  snap  at  it.  A  reddish  fluid  flowed  out  from 
their  tips  and  the  worm  was  dead  after  a  few  minutes  of 
violent  wriggling.  The  minute  pedicellarise  then  separated 
themselves  off  from  the  test  and  remained  imbedded  in 
the  worm.  They  all  broke  at  the  same  place,  just  at  the 
joint  between  the  base  of  the  spine  and  the  test,  and  some 
of  them  were  re-grown  in  about  a  month.  The  re-growth 
of  these  weapons  is  interesting,  and  it  may  be  recalled  that 
the  common  sea-urchin  (Echinus)  has  also  the  power  of 
regenerating  its  spines  and  these  only.  Because  of  the 
globular  nature  of  its  body  it  is  not  exposed  to  the  risk  of 
losing  parts,  and  we  can  thus  understand  why  it  does  not 
exhibit  autotomy  and  re-growth  on  the  scale  illustrated 
by  the  starfish  and  the  brittle-star. 

In  connexion  with  the  pedicellariae,  it  is  interesting  to 
notice  that  a  starfish  will  get  the  better  of  a  small  sea- 
urchin  by  applying  first  one  and  then  another  of  its  arms, 
to  the  spiny  surface,  getting  it  well  nipped  by  pedicellarise, 
and  then  wrenching  off  a  whole  crowd.  It  does  this  per- 
sistently over  and  over  again  until  the  sea-urchin  is  robbed 
of  all  its  weapons. 

As  an  illustration  of  armour  the  sea-urchin  might  also 
serve,  but  let  us  turn  to  Molluscs.  Every  one  who  knows 
the  molluscs  of  the  shore,  or  has  enjoyed  a  '  beauty-feast ' 
looking  over  the  cases  of  shells  in  a  museum,  must  have 
been  struck  with  the  solidity  of  many  of  these  encasements 
and  with  the  frequently  elaborate  outgrowths  from  the 
surface — knobs,  shelves,  roughnesses,  peaks,  undulations, 
and  what  not.  There  is  a  suggestion  of  sheer  exuberance 
about  many  of  them,  and  it  looks  as  if  there  were  a  waste 
of  shell-making  material  and  energy.  The  explanation  is 


64  THE  WONDER  OF  LIFE 

probably  in  part  physiological — though  as  yet  beyond 
statement — for  instance  that  the  deposition  of  conchin  and 
carbonate  of  lime  by  the  skin  or  mantle  may  be  an  organized 
way  of  dealing  with  the  waste  products  of  the  animal's 
body,  and  perhaps  also  with  by-products  of  digestion. 

This  must  remain  vague  in  the  meantime,  and  therefore  we 
turn  with  pleasure  to  a  secondary  or  oacological  explanation 
which  has  been  suggested  by  Mr.  Cyril  Crossland — that  the 
thickness  of  the  shell  and  the  outgrowths  on  it  must  be 
credited  with  protective  value.  The  shell-eating  fish 
Balistes  prefers  the  bivalves  with  weaker  shells.  Another 
enemy,  the  boring  gastropod  Murex,  kills  more  of  those 
with  smoother  shells.  It  kills  large  numbers  of  Margariti- 
fera  mauritii,  which  has  small  and  weak  outgrowths  on  its 
shell ;  it  kills  few  of  another  species,  Margaritifera  mar- 
garitifera,  which  has  large  strong  processes  remaining  for 
at  least  six  years.  It  seems  that  the  strong  processes  on 
the  surface  of  the  shell  prevent  the  Murex  from  readily 
getting  a  firm  hold  with  its  foot,  and  without  this  it  cannot 
work  the  drill  in  its  mouth  that  it  uses  to  bore  through 
the  bivalve's  defences.  In  some  species  of  bivalve  the 
outgrowths  of  tli3  shell  are  larger  in  the  young  forms,  and 
they  are  of  the  greater  value  therefore  during  the  relatively 
more  active  period  when  the  young  pearl  oyster,  or  hammer- 
shell  (Avicula),  or  Tridacna,  is  crawling  about  and  seeking 
a  suitable  place  for  settling  down  on.  Mr.  Crossland' s 
suggestion  may  require  modification,  but  he  backs  it  up 
with  definite  facts  showing  the  actual  life-saving  value 
not  of  the  armour  merely,  but  also  of  the  decorations  which 
it  bears. 

When  the  Murex  gets  a  good  grip  on  a  relatively  smooth 
shell  it  drills  a  hole  through,  and  allows  some  paralysing 


THE   HAUNTS   OF   LIFE  65 

mucus  to  enter  ;  but  there  is  a  quicker  method.  '  It  finds 
the  flexible  edge  of  the  shell,  then  by  contractions  of  its 
foot  breaks  a  piece  away.  The  mucus  of  the  foot  is  then 
poured  out  in  quantities,  and  this  has  some  poisonous  effect, 
as  the  bivalve,  while  still  untouched,  ceases  to  respond  to 
the  stimuli  which  ordinarily  cause  a  smart  closure  of  the 
shell  '.  If  the  shell  is  covered  with  rough  decoration  the 
Murex  finds  the  burglary  more  difficult. 

Infantile  Mortality.  —  The  shore  is  a  '  congested  dis- 
trict '  ;  the  birth-rate  is  high  ;  the  infantile  mortality  is 
enormous.  Under  the  ledges  of  the  rocks  and  in  the  crevices 
we  find  in  abundance  the  neat  little 
vase-like  cases,  we  may  almost  say 
cocoons,  which  the  dog-whelk  (Pur- 
pur  a  lapillus)  forms  for  its  eggs. 
They  change  from  a  light  pink  to  FIG.  20.—  Three  egg- 
a  straw  colour.  Each  is  the  scene 


of  a  tragedy.     If  we  examine  a  freshly          Purpura 

.  fastened     to      the 

formed  vase  we  find  that  it  contains  rock. 
scores  of  eggs.  Later  on,  we  find  only 
about  half  a  dozen  embryos.  What  has  become  of  the 
majority  ?  Careful  examination  at  intervals  shows  that 
some  of  the  eggs  get  the  start  of  others  in  their  development, 
and  that  the  leaders  devour  the  laggards,  and  continue  to 
lead  because  they  do  so.  The  same  is  true  in  the  egg- 
capsules  of  the  great  whelk  or  '  Buckie  '  (Buccinum 
undatum)  —  cases  reminding  one  of  the  fruits  of  hops, 
cemented  together  into  balls  often  the  size  of  an  orange, 
or  much  larger.  Inside  each  capsule  there  is  the  same 
grim  elimination  —  the  survivors  use  their  fellows  as  other 
embryos  use  the  yolk  of  the  egg.  There  is  no  lack  of 
brutal  frankness  in  some  of  Nature's  ways,  '  so  careful 

F 


66  THE  WONDER  OF   LIFE 

of  the  type  she  seems,  so  careless  of  the  single  life  ' ;  for 
here  we  have  cannibalism  in  the  cradle,  the  straggle  for 
existence  at  the  very  threshold  of  life. 

In  the  pool  where  we  gathered  the  Purpura  capsules,  we 
may  see  the  beautiful  Tubularians,  e.g.  Tubularia  indivisa, 
waving  their  tentacles,  and  it  is  interesting  to  remember  that 
in  the  ovary  of  Tubularia,  as  in  that  of  the  freshwater 
Hydra,  there  is  a  struggle  for  existence  among  the  numer- 
ous possible  eggs.  A  few  survive  in  Tubularia,  one  sur- 
vives in  Hydra ;  it  is  a  case  of  engulfing  the  other  ova. 
Thus  we  see  how  wide  the  conception  of  the  struggle  for 
existence  really  is — that  it  applies  even  to  the  germ-cells ; 
and  our  thoughts  pass  on  to  Weismann's  daring  speculation 
that  there  may  be  a  struggle  between  the  ancestral  con- 
tributions which  make  up  the  inheritance  within  the  egg. 

Speaking  of  '  infantile  mortality '  leads  us  naturally 
to  think  of  the  various  ways  in  which  it  is  lessened.  These 
show  an  interesting  parallelism  with  rational  methods  in 
operation  in  mankind.  The  first  method  is  to  transport  the 
delicate  young  lives  from  the  rough-and-tumble  life  of  the 
seashore  to  the  open  water.  Starfishes,  sea-urchins,  and 
their  allies,  many  worms  of  diverse  kinds,  many  crustaceans 
and  molluscs  have  delicate  larvaB,  altogether  unsuited  to 
stand  the  hard  conditions  of  the  shore,  but  admirably 
suited  for  a  period  of  pelagic  swimming  or  drifting.  It  is 
true  enough  that  Death  often  finds  them  there  also,  but 
they  are  certainly  much  safer  than  near  the  shore. 

It  is  an  interesting  question  whether  the  pelagic  habit 
of  the  larvae  of  some  shore  animals  is  an  indication  that 
the  cradle  of  the  stock  to  which  they  belong  was  the  open 
sea,  just  as  the  littoral  habit  of  the  robber-crab's  young 
is  an  indication  of  the  original  shore  home  of  this  terrestrial 


THE  HAUNTS  OF  LIFE  67 


FIG.  21. — Free-swimming  pelagic  larval  starfish — the  Bipinnaria  of 
Luidia — enormously  enlarged,  showing  transparent  larval  body  (A) 
with  curious  processes,  and  the  young  starfish  (B)  being  formed. 
(After  Mclntosh.) 


animal.  Or  is  it  a  quite  secondary  new  departure  on  the 
part  of  what  one  may  call  autochthonous  shore  animals, 
this  getting  their  young  into  a  relatively  safer  area  ?  Is 
it  similar  to  the  case  of  the  aquatic  habit  of  the  larvae  of 
many  insects,  such  as  gnats  and  mayflies,  which  is  believed 
to  be  quite  secondary  ?  There  is  most  to  be  said  for  the 
view  that  the  pelagic  phase  of  some  shore-animals  is 
secondary.  The  larvae  are  often  highly  specialized  in 
relation  to  open-sea  life,  and  not  the  least  like  ancestral 
forms.  In  certain  cases  the  first  view  may  be  enter- 
tained. 

Parental  Care. — Keturning  to  the  avoidance  of  infantile 
mortality,  another  method  of  life-saving  is  to  increase 
parental  care  and  nurture  ;  and  the  shore  is  rich  in  illus- 


68 


THE  WONDER  OF  LIFE 


trations  of  that.  One  of  the  British  starfishes,  Asterias 
mulleri,  seems  to  skip  the  usual  free-swimming  larval  stage, 
for  a  specimen  has  been  seen  on  the  shore  with  the 
miniature  young  ones  crawling  about  on  their  mother's 
body,  as  shown  in  the  subjoined  figure  of  one  of  the  Chal- 
lenger starfishes.  The  marine  leech,  or  skate-sucker,  lays 


FIG.  22. — A  starfish,  Leptoptychaster  kerguelensis,  with  the  young  ones 
(Y),  clambering  about  on  the  mother,  the  free -swimming  larval  stage 
having  been  suppressed.  (After  the  Challenger  Report.) 

its  eggs  in  the  empty  shell  of  a  bivalve  mollusc,  and  mounts 
guard  over  them  week  after  week,  carefully  removing  any 
mud  or  debris  that  might  smother  them.  In  a  number 
of  shore  crustaceans  the  young  are  carried  about  by  the 
mother,  and  may  move  about  on  her  body  in  a  very  quaint 


THE  HAUNTS   OF  LIFE 


69 


way,      now 
hanging       on 
to     her     an- 
tennae     and 
again   to   her 
tail.      It  is 
the  male  sea- 
spider     or 
Pycn  o  g  o      d 
that  gets  hold 
of    the     eggs 
and       carries 
them      about 
attached  to  a 
pair    of     ap- 
pendages, and 
it  is   likewise 
the  male  sea- 
horse (Hippo- 
campus)  who 
stows      away 
the  eggs  in  a 
c  apacious 
breast  pocket 
and       carries 
them       there 
till  they    are 
hatched. 

We  cannot 
exhaust  our 
admiration 
for  the  male 


V 

FIG.  23.— Nest  of  the  fifteen-spined  Stickleback, 
Gasterosteus  spinachia,  among  the  seaweed! 
E.  A  bunch  of  eggs.  (From  a  specimen.) 


70  THE  WONDER  OF  LIFE 

stickleback,  which  makes  a  nest  among  the  seaweeds,  and 
watches  over  his  offspring  with  a  remarkable  devotion.  At 
the  breeding  season  he  is  gorgeously  coloured  in  red,  orange 
and  green,  and  is  like  a  fragment  of  rainbow  in  the  pool. 
With  strange  glutinous  threads,  which  come  from  his 
kidneys,  he  ties  fronds  of  seaweed  together  into  a  nest 
with  an  entrance  and  an  exit  and  a  little  room  in  the  middle. 
Thither  he  manages  to  lead  his  mate,  who  lays  her  eggs 
in  the  nest  and  returns  to  everyday  pursuits.  The  male 
it  is  who  mounts  guard  and  drives  off  intruders,  often  much 
larger  than  himself — a  fine  example  of  a  big  soul  in  a  little 
body.  When  the  young  are  hatched,  like  animated  com- 
mas in  the  water,  his  labours  do  not  cease,  for  he  seems 
to  spend  his  day  in  tending  them — driving  them  in  at 
one  door,  only  to  see  them  reappear  forthwith  by  the  other. 
Another  striking  case  is  that  of  the  lumpsucker  or  cock- 
paidle  (Cycloptems  lumens],  a  quaint  sea-shore  fish  which 
has  its  pelvic  fins  shunted  forwards  and  transformed  into 
an  adhesive  sucker  which  takes  a  firm  grip  of  the  rocks. 
The  female  lays  a  large  mass  of  reddish  eggs  in  a  recess 
of  a  deep  rock-pool  about  the  low  tide-mark,  and  the  male 
mounts  guard  over  them.  He  becomes  greatly  excited 
at  the  approach  of  an  intruder,  but  what  is  even  more 
interesting  is  the  way  in  which  he  every  now  and  then 
lashes  his  tail  vigorously  from  side  to  side  close  by  the 
mass  of  eggs.  The  result  of  this  performance  is  that  the 
eggs  are  washed  free  of  the  mud  or  debris  that  settles  on 
them,  and  it  is  difficult  not  to  believe  that  the  lumpsucker 
is  aware  of  what  he  is  about.  He  has  been  known  to  guard 
the  eggs  so  anxiously  that  even  meals  were  neglected. 
The  infantile  mortality  may  be  lessened,  as  we  have 
seen,  by  a  migration  to  open  water,  or  by  an  increase  of 


THE  HAUNTS  OF  LIFE  71 

nurture.  It  may  be  counteracted,  though  not  lessened, 
by  enormous  multiplication ;  and  that  expedient  is  also 
familiar  on  the  shore.  A  single  oyster  may  have  sixty 
million  eggs — which  leaves  a  considerable  margin  for 
deaths.  We  may  recall  also  the  famous  case  of  the  palolo- 
worms  (Eunice  viridis)  of  the  coral-reefs  of  Samoa  and 
elsewhere.  Once  a  year,  with  striking  regularity,  myriads 
of  these  worms  crawl  out  tail  foremost  from  the  crevices 
they  inhabit,  and  agitate  themselves  so  violently  that 
while  the  head  end  remains  in  the  rock  the  posterior  ends 
drop  off  and  make  the  water  '  like  vermicelli  soup'.  These 
headless  worm-bodies  are  laden  with  egg-cells  and  sperm- 
cells,  and  these  are  shed  in  countless  millions  in  the  water, 
so  that  the  fertilization  is  quite  secure.  The  swarming 
begins  shortly  before  sunrise,  and  it  is  mostly  over  in  half 
an  hour.  Everything  is  extraordinary — the  sharp  punc- 
tuation of  the  time  of  reproduction  (different  in  Pacific 
and  Atlantic),  the  subtle  stimulus  of  the  moonlight  and 
the  sunrise,  the  discharge  of  the  multitudinous  writhing 
bodies,  the  profuse  sowing  of  the  seed ;  but  perhaps  the 
most  extraordinary  thing  is  the  evasion  of  the  death - 
penalty  which  reproduction,  especially  exuberant  repro- 
duction, often  involves  for  the  parent.  For  the  heads 
remain  in  the  reefs  and  grow  new  bodies  at  their  leisure. 
Given  stimulating  and  hazardous  conditions  of  life, 
and  keen  competition  among  organisms,  we  expect  to 
find  special  adaptations,  and  the  shore  is  full  of  them. 
We  have  already  referred  to  effective  armour,  such  as 
we  see  in  crab  and  whelk.  These  have  also  their  weapons 
and  so  have  many  of  the  unarmoured,  such  as  sea-anemones 
and  ribbon- worms  (Nemerteans).  Starfishes  and  brittle- 
stars  and  many  others  illustrate  the  adaptation  of  '  auto- 


72  THE  WONDER  OF  LIFE 

tomy '  or  self -mutilation,  losing  a  member  or  part,  but 
saving  the  whole  life,  and  able  at  leisure  to  regrow  what 
they  have  lost.  Protective  colour-resemblance  is  frequent, 
as  we  may  see  in  young  shore-crabs  (Carcinus  mcenas) 
which  show  many  different  colours  and  patterns,  and 
are  often  most  effectively  like  the  substratum  of  the  rock- 
pool  on  which  they  rest.  We  shall  discuss  later  on  the 
extraordinary  power  of  protective  colour-change  in  some 
prawns  (Hippolyte  varians),  and  that  of  young  flat-fishes, 
as  they  assimilate  themselves  to  the  sand  or  gravel,  is  not 
less  perfect,  though  within  a  narrower  radius.  The  sand- 
crab  (Hyas  araneus)  and  others  mask  their  carapace  with 
seaweed,  so  that  they  move  about  under  an  innocent 
disguise,  anticipating  on  their  own  line  such  human  tricks 
as  '  the  walking  wood  of  Birnam'.  And  this  is  only  the 
beginning  of  a  list  of  life-saving  adaptations  in  the  shore- 
area. 

We  cannot  pass  from  this  brief  study  of  the  littoral 
fauna  without  recalling  the  probability  that  it  was  on 
the  sea-shore  that  many  of  the  most  valuable  of  vital 
acquisitions  were  made.  Many  of  the  great  types  of 
animal  life  have  been  to  school  on  the  shore,  and  who 
shall  say  what  lessons  they  did  not  learn  amid  that  rough- 
and-tumble  life,  where  changes  come  often,  where  competi- 
tion is  keen,  where  the  discipline  of  dislodgment  is  ever 
recurrent,  where  a  premium  is  put  on  alertness  and  per- 
sistence and  adaptability  ?  The  shore  has  been  a  great 
school  of  life.  Yet  in  saying  this  we  do  not  wish  to  imply 
that  the  wisdom  of  any  animal  race  whatsoever  has  been 
due  to  the  premiums  which  individuals  have  paid  to 
experience.  For  this  theory  of  entailment  does  not  seem 
to  us  to  describe  Nature's  method. 


FIG.  24. — Animals  associated  with  Posidonia  Oceania,  a  sea-grass. 
Three  pieces  of  leaf  are  shown.  (After  Issel.)  A.  1 .  A  Hydroid, 
Plumularia  (Monotheca)  obliqua.  2.  An  Isopod,  Idothea 
hectica,  protectively  coloured.  3.  A  Bryozoon,  Membranipora 
pilosa,  and  small  patches  of  another,  Microporella  malusii.  B. 

4.  A  small  fish,  Lepadogaster  bimaculatus,  protectively  coloured. 

5.  Growth  of  coralline,  a  calcareous  Alga.     C.    6.  Membrani- 
pora.    7.  A  Hydroid,  Sertularia  mediterranea. 


72 


THF 


tomy'  or  self- 
saving  the  wh 
they  have  lost 
as  we  may  'JH 
which   sho 
are  often  i 
pool  on  w. 
extra---1 


but 

it  Insure  vhat 

'Qt, 

>dnus  mcsnas) 

re   and   patterns,  and 

:(>stratum  of  the  rock- 

'.'•  •    >::all  discuss  later  on  the 

olour-change  in  some 

that  of  young  flat-fishes, 

gravel,  is  not 

.  rrowei  s>e  sand- 

.r-  mask  their  caraace  with 


,boqoal     nA  .S 
rS  .noo^a 
.a      ii8uIEm  Blb.oqor.iM 


B«pHdo    ^rliono 
A  .£    ,* 
.Wiohs  ^o 


- 

, 


an  iti  . 
shall  - 
and-tiunc 
tion  is   k^' 
recurrent,  v 
sistence  an" 
school  of  life.      ; 
that  the  wisdou 

experience.    For  this 


A 


"3   of 
aQd  wno 

.  ai  dd  that  rough- 

-      where  competi- 

islodgment is  ever 

'"rtness  and  per- 

a been  a  great 

-t  wish  to  imply 

-  een 

1  to 


THE  HAUNTS  OF  LIFE  73 

Peculiar  Conditions. — There  are  many  peculiar  haunts 
of  life  which  must  be  regarded  as  subdivisions  of  the  main 
haunts,  though  they  have  come  to  have  very  little  in  com- 
mon with  any  one  of  them.  Thus  we  find  a  peculiar  set 
of  animals  in  the  salt  marshes  which  occur  here  and  there 
along  the  coasts  ;  in  continental  salt  lakes  which  have 
no  connexion  with  any  present  sea  ;  in  hot  springs  where 
animals  may  sometimes  be  found  flourishing  at  a  tem- 
perature of  45°C. 

II.    THE  PELAGIC  FAUNA 

The  conditions  of  life  for  open-sea  or  pelagic  animals 
must  be  regarded  as  on  the  whole  very  favourable.  For 
there  is  plenty  of  room  and  there  are  no  boundaries  to 
be  dashed  against  till  a  shore  is  reached.  A  storm  can 
be  avoided  by  sinking  for  several  fathoms.  There  is  sun- 
shine without  any  risk  of  drought,  and  more  uniformity 
throughout  the  day  and  throughout  the  year  than  is  to 
be  found  elsewhere  except  in  the  monotonous  abysses  of 
the  deep  sea.  The  extraordinary  abundance  of  micro- 
scopic Algae  at  the  surface  and  down  for  many  fathoms 
ensures  an  inexhaustible  food  supply  for  the  animals. 
There  is  unlimited  '  sea-soup  '.  It  is  not  surprising,  there- 
fore, to  find  that  the  open  sea  has  been  peopled  from  the 
earliest  times  of  which  the  fossil-bearing  rocks  give  us 
any  record. 

Dr.  J.  Y.  Buchanan,  who  has  given  much  attention 
to  the  study  of  the  colour  of  the  sea,  points  out  that  a 
deep  olive-green,  common  in  polar  latitudes,  but  not 
confined  to  them,  is  due  to  an  abundance  of  diatoms  and 
to  the  excretions  of  animals  that  live  on  diatoms.  From 
the  polar  ice  to  beyond  the  fortieth  parallel,  the  surface 


74  THE  WONDER  OF  LIFE 

water  is  a  pronounced  indigo  colour.  From  the  equator 
to  beyond  the  thirtieth  parallel,  the  colour  of  the  surface 
water  is  a  pure  and  brilliant  ultramarine.  The  olive- 
green,  the  indigo  and  the  ultramarine  are  the  three  great 
colour-types  of  the  sea. 

Open  Sea. — One  must  be  careful  to  notice  that  pelagic 
does  not  mean  at  the  surface ;  it  means  '  open  sea  '  and 
as  far  down  as  clear  light  reaches.  Many  small  organisms 
have  their  maximum  at  a  depth  of  50  fathoms  below  the 
surface,  and  a  great  advantage  of  being  several  fathoms 
down  is  that  a  measure  of  calm  is  enjoyed.  Dr.  A.  G. 
Mayer  brings  this  out  very  vividly  in  his  memoir  on  the 
Ctenophores  or  '  sea-gooseberries  '  of  the  Atlantic  coasts 
of  North  America — fascinatingly  beautiful  animals  of 
the  Ccelenterate  series,  distantly  related  to  Medusoids. 

'  In  the  extreme  tenuity  of  their  bodily  substance  and 
their  diaphanous  delicacy  of  coloration,  the  ctenophores 
stand  apart  from  other  marine  animals.  Their  presence 
in  the  water  is  commonly  denoted  only  by  the  brilliant 
flash  of  rainbow  colours,  which  play  along  the  lines  of 
their  ciliary  combs  as  they  move  languidly  beneath  the 
unrippled  surface  of  the  sea.  Yet  these  creatures  are 
no  more  wonderful  in  their  complex  organization  than 
in  their  remarkable  adjustment  to  their  habitat :  for  so 
delicate  are  most  of  them  that  a  current  such  as  that  of 
an  oar  suffices  to  tear  them  into  misshapen  shreds — a  fate 
which  they  escape  in  time  of  storm  by  sinking  far  into 
the  depths.  This  fact  accounts  for  the  extreme  rarity 
of  many  of  these  forms,  for  the  ocean's  surface  must  have 
remained  flat  as  a  mirror  for  many  hours  before  they  can 
be  lured  upward  from  the  calm  of  their  deep  retreat.' 

We  must  distinguish  between    the    surface    plankton 


THE  HAUNTS  OF  LIFE  75 

and  the  sub-surface  plankton,  both  within  the  light- limit, 
and  the  bathy-plankton  which  extends  below  that  limit, 
and  consists  necessarily  of  animals  only. 

Swimmers  and  Drifters. — The  open- water  animals 
(Plankton,  in  the  wide  sense)  are  conveniently  divided 
into  the  active  swimmers,  such  as  fishes,  which  make  up 
the  Nekton,  and  the  more  passive  drifters,  with  relatively 
feeble  organs  of  locomotion  or  none  at  all,  that  are  swept 
about  at  the  mercy  of  tides  and  currents.  Another  general 
distinction  should  be  borne  in  mind, — that  between  the 
permanent  and  the  temporary  planktonic  animals,  for 
while  there  are  many  creatures  that  spend  their  whole 
existence  in  the  open  sea,  such  as  Ctenophores  and  Portu- 
guese Men  of  War,  there  are  others,  which  are  only  there 
as  larvae,  e.g.  the  swimming  bells  of  littoral  zoophytes,  and 
the  young  stages  of  many  worms,  echinoderms  and  molluscs. 

Representative  Pelagic  Animals. — The  pelagic  fauna 
is  made  up  of  a  great  variety  of  types,  from  the  pin-head- 
like  Noctiluca,  whose  intense  luminescence  sets  the  waves 
aflame  in  the  short  summer  darkness,  to  the  great  whales 
— the  giants  of  the  present  age.  The  list  includes  many 
Foraminifera  (especially  the  Globigerinids),  thousands 
of  different  kinds  of  Radiolarians  (so  successful  perhaps 
because  they  have  partner  Algse  living  inside  them),  the 
active  Dinoflagellates  (much  sought  after  by  small  crus- 
taceans and  even  by  fishes),  many  other  Infusorians,  jelly 
fishes  or  Medusae,  often  in  great  fleets,  and  the  swimming- 
bells  or  Medusoids,  many  of  which  are  the  liberated  repro- 
ductive buds  of  sedentary  zoophytes,  strange  colonies 
known  as  Siphonophores  such  as  the  Portuguese  Man  of 
War  and  Velella,  the  delicate  Ctenophores  which  never 
come  to  the  surface  unless  it  is  very  calm,  not  a  few  free- 


76 


THE  WONDER  OF   LIFE 


swimming  '  worms',  such  as  Sagitta — like  a  glass  arrow 
in  the  water,  a  few  Holothurians  or  sea-cucumbers  which 
have  departed  widely  from  the  prevalent  habit  of  their 
class,  a  legion  of  Crustaceans  often  of  surpassing  beauty 
of  colour  and  form,  a  few  insects 
(Halobatidse)  the  last  creatures 
one  would  expect,  such  molluscs 
as  the  sea-butterflies  (Pteropods) 
— dainties  which  the  whalebone 
whale  captures  in  countless 
myriads  in  the  great  sieve  which 
hangs  down  from  the  yawning 
cavern  of  its  mouth,  the  similarly 
light-shelled  or  shell-less  Hetero- 
pods  and  many  actively  swimming 
cuttlefishes,  such  as  the  Argonaut, 
some  Tunicates  like  the  Salps 
(often  swimming  gently  in  long 
transparent  chains)  and  the 
'  fire-flame  '  (Pyrosoma)  famous 
for  its  luminescence,  numerous 
fishes  such  as  flying  fishes,  a  few 
turtles  and  venomous  sea-snakes, 
such  birds  as  Mother  Carey's 
Chickens  and  the  flightless  pen- 
guins, and  among  mammals  the  cetaceans  large  and  small. 
This  abbreviated  roll  may  serve  to  suggest  the  representative 
character  of  the  pelagic  fauna.  Within  the  pelagic  fauna  it 
seems  right  to  include  the  petrels,  since  they  are  distinc- 
tively ocean-wanderers,  and  very  seldom  come  ashore 
except  for  breeding.  An  ancient  race,  marked  by  their 
protruding  tubular  nostrils  and  their  compound  bill  of 


FIG.  25.— Halobates,  a 
pelagic  insect,  one 
of  the  Hemiptera. 
(After  Buchanan 
White.) 


THE  HAUNTS   OF  LIFE  77 

several  horny  plates  separated  by  deep  grooves,  the  petrels 
appear  to  have  been  very  successful,  for  they  are  to  be 
found  in  all  the  oceans — including  the  Arctic  and  Antarctic 
— and  they  are  represented  by  a  great  variety  of  types  from 
the  tiny  storm  petrel  to  the  gigantic  albatross  which  may 
have  a  spread  of  wing  twice  the  height  of  a  man.  As  we 
have  already  said,  there  are  many  larval  forms  of  shore 
animals  which  pass  through  a  pelagic  phase.  They  cannot 
be  counted  in  except  for  the  time  being,  and  the  same 
must  be  said  of  the  Leptocephali  or  transparent  young 
stages  of  various  eels.  Nor  can  we  include  such  fishes 
as  salmon  and  sea-trout,  which  really  belong  to  the  fresh 
waters,  though  so  much  of  their  energy  is  acquired  during 
their  visits  to  the  sea.  There  are  some  pelagic  animals, 
such  as  the  arrow- worms  (Sagitta  and  the  like),  which  we 
can  think  of  as  having  always  lived  in  the  open  sea,  but 
most  seem  to  bear  the  impress  of  lessons  which  the  open 
sea  could  never  have  taught  them.  In  such  a  case  as 
the  Halobatidse  (pelagic  insects)  it  is  obvious  that  the 
open  sea  is  a  secondary  home. 

Adaptations. — Among  the  adaptations  to  pelagic  life, 
the  following  seem  most  important.  In  several  ways  the 
floating  capacity  is  increased  :  by  the  formation  of  gas 
reservoirs,  such  as  the  great  float — like  a  glorified  cock's- 
comb — of  the  Portuguese  Man  of  War  ;  by  the  development 
of  light  and  buoyant  tissue,  as  in  the  jelly  of  Medusae  ; 
and  by  the  enormous  development  of  delicate  outgrowths 
which  give  the  creature  a  wide  surface  of  contact  with 
the  water,  as  we  see,  for  instance,  in  many  of  the  pelagic 
Crustaceans.  We  cannot  glance  at  them  without  feeling 
that  architecture  of  this  sort  could  not  survive  the  sea- 
shore conditions  for  a  day. 


78  THE  WONDER  OF  LIFE 

Many  open-sea  animals  are  transparent ;  many  of  those 
that  live  near  the  surface  have  beautiful  blue  and  violet 
colours,  well  seen  in  the  Siphonophore  Velella  and  in  the 
Gasteropod  lanthina.  It  is  possible  that  there  is  occasion- 
ally some  adaptiveness  in  the  transparency,  though  this 
quality  follows  for  the  most  part  from  the  lightness  of 
build.  It  must  in  some  cases  make  the  swimmers  or 
drifters  practically  invisible.  Even  in  a  small  bowl  of 
sea- water  it  is  very  difficult  to  see  an  arrow-worm  (Sagitta) 
or  the  like,  and  it  is  very  interesting  to  watch  in  a  large 
aquarium  how  the  quite  unique  Venus's  girdle  (Cestus 
veneris),  which  is  at  once  transparent  and  iridescent,  is 
conspicuous  at  one  moment — a  creature  of  positively  daz- 
zling beauty — and  invisible  the  next.  Some  pelagic 
fishes,  such  as  a  quaint  little  sea-horse,  which  live  among 
the  Sargasso  weed,  have  the  body  reddish  brown,  but  the 
fins,  which  are  spread  out  in  the  open  water,  are  a  beautiful 
transparent  blue.  It  is  no  argument  against  the  theory 
that  transparency  is  advantageous  to  point  out  that  it 
is  often  of  no  avail,  e.g.  when  the  great  Cetacean  catches 
thousands  of  sea-butterflies  in  its  net. 

There  is  evidently  a  considerable  intensity  of  life  in 
some  of  the  Plankton  animals,  for  their  movements  are 
practically  ceaseless,  and  their  sensory  equipment,  especi- 
ally in  the  way  of  eyes  and  balancing  organs,  is  often  very 
remarkable.  Many  are  '  phosphorescent ',  such  as  Nocti- 
luca,  Ctenophores,  Pyrosoma,  but  the  vital  significance 
of  this  remains  a  riddle.  Many  move  about  in  shoals, 
which  indicate  prolific  reproduction  and  great  abundance 
of  food.  The  numbers  are  greatest  in  the  colder  seas, 
which  is  probably  due  to  the  fact  that  at  low  temperatures 
growth  and  development  are  slowed,  the  life  is  drawn  out, 


THE  HAUNTS   OF  LIFE  79 

and  more  generations  are  living  at  the  same  time.  In 
some  cases  the  large  number  of  different  species,  within 
a  relatively  narrow  radius,  is  very  characteristic.  Thus 
there  are  over  5,000  species  of  Radiolarians.  This,  per- 
haps, means  that  the  conditions  of  life  are  relatively  easy 
and  Natural  Selection  not  very  stringent. 

There  is  much  still  to  learn  in  regard  to  the  vital  economy 
of  the  sea,  for  instance  as  to  the  food  supply.  It  has 
been  calculated  by  Putter  and  Dakin  that  the  '  producers  ' 
(the  plant-plankton)  are  often  insufficient  for  the  '  con- 
sumers '  (the  animal  plankton),  and  Dr.  Dakin  has  also 
maintained  that,  even  if  there  were  enough  of  food,  it 
would  be  '  an  altogether  unthinkable  piece  of  work '  for 
the  animal  to  catch  enough  to  cover  its  physiological 
expenditure.  Dr.  Dakin  calculates  that  a  sponge  sixty 
grammes  in  weight  would  require  to  filter  several  thousand 
times  its  own  volume  of  water  per  hour  in  order  to  obtain 
sufficient  food,  which  sounds  a  somewhat  formidable 
task.  A  big  jellyfish,  he  calculates,  would  require  over 
seven  millions  of  nauplius  larvae  per  day,  which  is  literally 
a  large  order.  '  It  is  quite  impossible  for  such  large  quanti- 
ties to  be  caught,  and  equally  strange  that  remains  of  the 
creatures  are  so  rarely  found,  if  they  have  been  captured 
as  food  '.  Perhaps  it  is  too  soon,  however,  to  be  very 
confident  in  regard  to  the  amount  of  organic  material  that 
a  creature  like  a  sponge  or  jellyfish  requires  to  cover  the 
loss  due  to  its  metabolism. 

Prof.  Piitter's  view  is  that  many  marine  animals  are 
in  a  way  saprophytic — feeding  on  the  organic  compounds 
contained  in  solution  in  the  water.  He  regards  the  sea 
as  a  great  reservoir  of  dissolved  foodstuffs  (compounds 
of  carbon  other  than  carbonates,  and  compounds  of  nitrogen 


8o  THE  WONDER  OF  LIFE 

other  than  ammonia,  nitrates  and  nitrites).  The  question 
is,  how  much  of  this  foodstuff  there  really  is;  and  here 
the  doctors  differ.  It  is  quite  possible  that  organs  with  a 
large  surface,  notably  gills,  have  a  directly  nutritive  value. 
Prof.  Putter's  strongest  argument  is  simply  that  the  solid 
food-supplies  taken  in  by  various  types — e.g.  sponge  and 
crustacean — are  not  sufficient  to  account  for  the  chemical 
changes  that  are  known  to  go  on.  But  the  comparative 
physiology  of  marine  invertebrates  is  still  very  young.  In 
any  case  we  must  not  too  hurriedly  dismiss  the  idea  that 
there  may  be,  especially  in  crowded  zones,  a  sort  of  perma- 
nent '  stock  '  to  the  sea-soup.  Every  one  who  has  examined, 
even  with  the  fingers,  the  foam  that  is  blown  ashore  from 
a  rich  littoral  region  after  a  storm,  will  agree  that 
there  may  be  much  dissolved  organic  matter  in  the  water. 
But  this  is  no  matter  for  opinion.  It  remains  to  be  seen, 
by  careful  analysis  and  after  elimination  of  all  the  plankton, 
how  far  it  is  true  that  there  is  bread  in  the  waters. 

Recent  investigations  at  Port  Erin  Biological  Station, 
by  Prof.  Benjamin  Moore  and  others,  have  not  in  the  least 
confirmed  Putter's  view.  Of  great  importance  beyond 
doubt  in  the  economy  of  the  sea  are  the  extremely  minute 
organisms  of  the  '  dwarf  plankton,'  so  small  that  they 
pass  through  the  interstices  of  fine  silk  cloth  (see 
Fig.  34). 

There  are  very  interesting  seasonal  variations  in  the 
amount  of  the  Plankton,  the  two  maxima  being  in  spring 
and  autumn.  Waves  of  abundance  follow  one  another 
in  a  regular  order ;  thus  there  is  usually  to  begin  with 
a  great  multiplication  of  Diatoms,  then  of  Dinoflagellata, 
and  then  of  Copepods.  The  reasons  for  the  seasonal  varia- 
tions are  still  being  investigated,  but  there  is  indication 


THE  HAUNTS   OF  LIFE  81 

that  the  spring  exuberance  depends  largely  on  the  sun- 
light, and  partly  on  the  temperature  of  the  water  and 
vertical  currents  in  the  sea  which  aid  in  the  circulation 
of  food  materials. 


III.    THE  ABYSSAL  FAUNA 

Every  one  has  seen  more  or  less  of  the  other  haunts  of 
life,  but  no  one  has  had  any  vision  of  the  Deep  Sea — the 
abyssal  region  beyond  the  light  limit  and  the  plant  limit. 
Many  have  been  within  a  stone's  throw,  or  drop  rather, 
of  it ;  a  few  have  had  the  rare  experience  of  dredging 
from  its  distant  floor  ;  many  have  examined  Deep-Sea 
animals  in  museums  ;  but  no  one  has  ever  seen  its  secrets 
in  their  natural  setting. 

The  study  of  the  Deep  Sea  is  relatively  modern,  but 
its  progress  has  been  strikingly  rapid.  In  1818  Sir  John 
Ross  dredged  a  brittle-star  (Astrophyton)  from  800-1,000 
fathoms,  but  this  discovery  appears  to  have  supplied  no 
stimulus.  In  1841  Edward  Forbes  dredged  without 
result  in  deep  water  in  the  Mediterranean,  and  Sir  James 
Ross's  similar  attempts  in  1847  were  not  more  successful. 
Naturalists  of  the  middle  of  the  nineteenth  century  spoke 
of  the  Deep  Sea  as  an  abyss  where  life  is  either  extinct,  or 
exhibits  but  a  few  sparks  to  mark  its  lingering  presence. 
In  1860,  however,  when  the  cable  from  Sardinia  to  Algiers 
was  lifted  for  repair  from  a  depth  of  1,000  fathoms,  fifteen 
animals  were  found  attached  to  it — a  discovery  which  fired 
enthusiasm.  Surgeon-General  Wallich  should  be  remem- 
bered, we  think,  as  one  of  the  early  pioneers,  along  with 
W.  B.  Carpenter,  Huxley  and  Wyville  Thomson.  The 
cruises  of  the  Lightning  (1868)  and  the  Porcupine  (1870) 

G 


82  THE  WONDER  OF  LIFE 

showed  that  most  of  the  invertebrate  types  were  represented 
at  depths  of  600  fathoms  or  more.  These  preliminary 
samplings  led  on  to  the  famous  voyage  of  the  Challenger 
(1872-76),  which,  like  Darwin's  voyage  on  the  Beagle, 
may  be  ranked  as  a  Columbus  voyage  in  the  history  of 
biology.  Darwin's  voyage  led  to  the  discovery  of  a  new 
world — for  the  evolution  idea  made  everything  new ;  the 
Challenger  voyage  led  practically  to  the  discovery  of  the 
new  world  of  the  Deep  Sea.  Under  Wyville  Thomson's 
leadership  the  explorers  cruised  for  three  and  a  half  years 
over  the  wide  oceans,  crossing  the  Atlantic  rive  times, 
covering  68,900  nautical  miles,  reaching  down  with  the 
long  arm  of  the  dredge  to  depths  equal  to  reversed  Hima- 
layas, raising  treasures  of  animal  life  from  over  five  hundred 
stations,  and  bringing  home  spoils  which  have  taken  forty 
huge  volumes  to  describe.  The  results,  under  Sir  John 
Murray's  editorship,  have  supplied  a  broad  foundation 
for  the  science  of  oceanography,  and  given  a  powerful  and 
lasting  impulse  to  zoology  in  general. 

Without  dwelling  on  historical  facts,  we  venture  to  call 
attention  to  three  points.  (1)  It  was  out  of  a  practical 
task  that  the  stimulus  to  Deep-Sea  exploration  arose, 
and  there  has  been  on  the  part  of  science  some  repayment 
of  this  debt.  (2)  What  happened  is  a  warning  against 
dogmatism.  It  is  not  very  long  since  an  authority  spoke 
of  the  floor  of  the  Deep  Sea  as  '  an  area  regarding  which 
nothing  was  known,  nor  could  be  known  ' ;  and  now  there 
is  a  large  library  of  descriptive  reports.  (3)  What  the 
Challenger  began  has  been  followed  up  by  expeditions 
from  most  of  the  countries  of  Europe  and  by  the  magnifi- 
cent work  of  the  late  Professor  Alexander  Agassiz  in 
America. 


FIG.  27.— Deep-sea  Crinoid  (Metacrinus),  showing  the  attaching   *  roots '   (R),  the 
stalk  (ST)  g1vmg  oft    cirri '  (ci),  and  the  calyx  (CA)  with  ten  feathered  arms  (A). 


THE   HAUNTS  OF   LIFE  83 

Physical  Conditions 

(1)  Depth. — The  average  depth  of  the  sea  is  about  2| 
miles,  and  over  80  per  cent,  of  the  sea-floor  lies  at  a  depth 
of  over  a  thousand  fathoms.     Thus  the  greater  part  of  the 
Deep  Sea  is  very  deep.     It  is,  indeed,  a  remarkable  fact 
that  the  great  abyssal  plain,  deeper  than  1,700  fathoms, 
extends  over  about  100  millions  of  square  miles,  which  is 
more  than  a  half  of  the  entire  superficial  area  of  the  earth 
(197  million  square  miles,  of  which  57  millions,  say  30  per 
cent.,  are  terrestrial,  and  140  millions,  say  70  per  cent., 
are  marine). 

Here  and  there  in  the  Deep  Sea  there  are  tremendous 
depths,  technically  called  '  deeps',  of  over  3,000  fathoms  ; 
and  eight  soundings  of  over  5,000  fathoms  have  now  been 
taken.  Among  these  is  the  famous  '  Challenger  deep ' 
in  the  North- West  Pacific,  of  5,269  fathoms,  nearly  six 
miles,  in  which  Mount  Everest  would  be  more  than  en- 
gulfed. In  fact,  its  summit  would  be  2,600  feet  below  the 
surface.  Another  instance  is  the  '  Swire  deep  ',  off  Min- 
danoa,  of  5,348  fathoms,  over  six  miles,  in  which  Mount 
Everest  might  be  submerged  with  3,087  feet  to  spare.  It 
is  easy  to  calculate  the  vertical  distance  between  the  top 
of  Mount  Everest  and  the  foot  of  the  Swire  deep. 

(2)  Pressure. — From  the  weight  of  water,  which  great 
depth  implies,  it  follows  that  there  must  be  enormous 
pressure  in  the  Deep  Sea.    At  2,500  fathoms  it  is  2|  tons  on 
the  square  inch,  perhaps  twenty-five  times  as  much  as  the 
pressure  in  the  cylinder  of  an  engine  that  drives  an  average 
railway  engine.     Even  the  water  is  compressed  and  bodies 
into  which  the  water  cannot  penetrate  quickly  enough  are 
squeezed  almost  beyond  recognition  when  they  are  sunk 


84  THE  WONDER   OF  LIFE 

to  great  depths.  The  Challenger  explorers  found  that  a 
piece  of  wood  sunk  to  the  abysses  was  so  heavy  when 
pulled  up  again  that  it  sank  in  water.  The  muscles  of  a 
dead  animal,  such  as  a  whale,  must  undergo  a  tremendous 
compression  if  the  carcass  sinks. 


FIG.  28. — Deep-Sea  Pycnogonid  or  "  Sea  Spider,"  Pipetta,  with  extra- 
ordinary length  of  limb  in  proportion  to  the  size  of  the  body.  The 
males  carry  the  eggs.  (After  Loman .) 

When  a  whale  fills  its  lungs  and  '  sounds ',  remaining 
below  the  surface  for  ten  minutes  at  a  time  (as  the  Prince  of 
Monaco  proved),  its  body  may  be  subjected  to  a  consider- 
able increase  of  pressure,  which  the  ribs  in  particular  have 
to  withstand.  Mr.  J.  Y.  Buchanan  suggests  that  the 
occurrence  of  a  number  of  broken  and  repaired  ribs  on  one 


THE   HAUNTS   OF   LIFE  85 

side  of  a  whalebone  whale's  skeleton  preserved  in  the 
Museum  of  Monaco  may  be  a  record  of  the  animal's  having 
gone  beyond  the  limit  of  safety.  He  recalls  Paul  Bert's 
experiment,  in  which  the  pressure  of  the  air  in  the  lungs  of 
a  dog  was  reduced  by  a  not  very  large  fraction  of  an  atmo- 
sphere, with  the  result  that  the  thorax  collapsed  with 
every  rib  broken. 

(3)  Temperature. — The  sun's  heat  is  lost  at  about  150 
fathoms,  and  the  Deep  Sea  is  therefore  intensely  cold. 
With  relatively  little  variation  (2°  or  3°  Fahr.)  in  the  year, 
the  temperature  remains  near  the  freezing  point  of  fresh- 
water (32°  Fahr.).  The  bottom  temperature  may  be  below 
30°  Fahr.  in  Polar  waters,  and  over  90  per  cent,  of  the  whole 
sea-floor  it  may  be  said  that  an  eternal  winter  reigns. 
What  a  contrast  this  is  to  the  surface  conditions,  which 
may  show  an  annual  variation  of  50°  in  one  area,  and  which 
show  such  extremes  as  26°  Fahr.  off  Nova  Scotia  and  96°  in 
the  Persian  Gulf !  The  variations  and  extremes  on  land 
are  still  more  marked. 

The  coldness  of  the  deep  water  seems  to  be  mainly  due 
to  a  flow  of  cold  bottom-water  from  the  Southern  and 
Antarctic  oceans  towards  the  equator,  and  in  a  less  degree 
to  a  similar  flow  from  the  sub- Arctic  region.  The  causes 
of  this  flow  are  complex,  but  the  oceanographers  refer  to 
the  great  intertropical  evaporation,  to  the  action  of  extra- 
tropical  winds  which  blow  the  surface-waters  polewards, 
to  '  the  head  of  water '  which  is  accumulated  in  high  lati- 
tudes by  the  action  of  the  prevailing  winds,  and  to  the 
greater  density  of  the  water  in  high  latitudes.  As  temper- 
ature affects  the  solubility  of  gases  in  water,  cold  water 
being  able  to  absorb  more  than  warm  water,  the  polar 
waters  contain  more  oxygen  than  elsewhere,  and  the 


86  THE  WONDER  OF  LIFE 

equatorial  movement  of  bottom- water  rich  in  oxygen  must 
be  of  considerable  biological  importance  for  the  animals  of 
the  Deep  Sea. 

(4)  Darkness. — There  is  but  little  penetration  of  light 
beyond  250  fathoms,  so  that  the  world  of  the  Deep  Sea  is 
in  utter  darkness,  save  only  in  so  far  as  that  is  relieved  by 
gleams  of  '  phosphorescent '  light.     In  some  places  where 
there  is  much  of  this  luminescence,  it  may  be  that  the 
scene  is  like  the  ill-lighted  suburbs  of  a  town  on  a  very  dark 
night,  or  like  a  moorland  with  no  light  save  from  the  stars. 
In  his  1911  cruise  on  the  Michael  Sars,  the  late  Sir  John 
Murray  found  that  the  light  limit  had  been  under-esti- 
mated.    By  using  more  delicate  apparatus,  notably  the 
Helland-Hansen  photometer,  he  was  able  to  show  that 
there  is  a  clear  effect  at  300  fathoms,  and  some  effect  at 
500  fathoms,  which  is  about  half  a  mile  down.     At  900 
fathoms  no  effect  of  light  was  detectable.     These  were 
very  sensitive  tests,  however,  and  for   practical   purpose 
we  may  still  say  that  there  is  very  little  light  below  250 
fathoms. 

(5)  Calm  and  Silent. — Another  physical  feature  is  the 
pervading  calm,  for  the  severest  storms  are  shallow  in 
their  grip,  and  though  the  cold  polar  water  is  ever  creeping 
along  the  bottom  towards  the  equator,  this  is  a  relatively 
slow  movement.     Only  in  a  few  places  is  there  evidence  of 
what  may  be  called  a  current.     If  there  were  rapid  move- 
ment the  deep  ooze  which  covers  vast  areas  of  the  sea-floor 
would  be  raised  in  whirling  clouds.     Thus  we  must  think 
of  the  deep  sea  as  extraordinarily  still  and  quiet,  for  there 
can  be  no  noise  to  break  the  abiding  silence  of  the  abysses. 

(6)  Monotony. — There  is  some  variety  in  the  composi- 
tion of  the  sea-floor,  for  the  remains  of  calcareous  organisms 


THE  HAUNTS   OF  LIFE  87 

predominate  in  some  places  and  of  siliceous  organisms  in 
others,  and  the  debris  called  '  red  clay  '  is  found  in  the 
deepest  parts  of  all.  But  otherwise  monotony  prevails. 
There  is  no  scenery,  except  that  here  and  there  a  ridge 
stretches  like  a  watershed,  or  a  volcanic  cone  rises  abruptly 
to  the  surface,  or  a  great  depression  leads  into  one  of  the 
'  deeps'.  Otherwise  there  are  great  stretches  of  undulating 
plain,  like  very  flat  sand-dunes,  or  like  a  great  desert. 
There  is  no  sound  and  echo,  no  day  and  night,  no  summer 
and  winter  in  the  monotonous  Deep  Sea.  It  is  all  silence, 
all  night,  all  winter.  Apart  from  the  animals  altogether, 
what  a  remarkable  picture  rises  in  the  mind — a  picture  of 
the  forever  unseen — a  strange,  dark,  cold,  calm,  silent, 
monotonous  world! 


Biological  Conditions 

(a)  The  first  big  fact,  the  establishment  of  which  we  owe 
to  the  Challenger  expedition,  is  that  there  is  practically  no 
depth-limit  to  the  distribution  of  animal  life.  Wherever 
the  long  arm  of  the  dredge  has  been  able  to  reach,  there 
are  organisms  and  plenty  of  them.  It  is  astonishing  to 
read  of  Sir  John  Murray  and  Dr.  Hjort  using  an  otter 
trawl,  with  fifty  feet  of  spread,  at  a  depth  of  2,820  fathoms 
(over  three  miles),  and  using  it  very  successfully.  It 
should  be  noticed  that  there  are  some  thinly  peopled 
areas — sea-floor  deserts,  so  to  speak  ;  that  there  is  a  richer 
population  at  the  more  moderate  depths;  that  there  are 
more  animals  on  the  calcareous  ooze  than  elsewhere;  and 
that  there  are  probably  thinly-peopled  zones  between  the 
bottom  and  the  light-limit.  But  the  big  fact  is  that  there 
is  no  '  deep  '  too  deep  for  life. 


88  THE  WONDER  OF  LIFE 

(6)  Plantless. — The  second  big  fact  is  that,  beyond  the 
sunk  resting  stages  of  some  simple  Algse,  there  are  no  plants 
in  the  Deep  Sea.  This  follows  from  the  absence  of  light, 
and  it  involves  as  a  consequence  that  all  the  Deep-Sea 
animals  must  be  either  carnivorous  or  devourers  of  debris. 
There  are  the  usual  '  nutritive  chains  ' — abyssal  fish  eating 
abyssal  crustacean,  and  that  eating  worm,  and  that  eating 
still  smaller  fry  ;  but  since  they  cannot  all  be  eating  one 
another  there  must  be  some  extraneous  food-supply.  That 
is  afforded  by  the  gentle  and  ceaseless  rain  of  small  organ- 
isms, killed  by  vicissitudes  in  the  pelagic  meadows  over- 
head, and  sinking  through  the  miles  of  water  like  snow- 
flakes  falling  on  a  very  still  day.  Investigation  all  goes  to 
show  that  while  big  corpses  like  those  of  fishes  are  doubt- 
less all  to  the  good  if  they  reach  the  bottom  undevoured, 
what  counts  for  the  Deep-Sea  basal  food-supply  is  the  rain 
of  microscopic  atomies. 

(c)  No  Bacteria. — There  are  abundant  bacteria  in  the 
sea,  in  the  economy  of  which  they  play  a  very  important 
role,  but  there  seem  to  be  none  in  the  great  abysses.     It  is 
interesting  to  know  of  one  place  in  the  wide  world  where 
there  are  no  microbes.     From  their  absence  it  follows  that 
there  is  no  rottenness  ;  everything  is  devoured  in  the  great 
clearing-house.     The  whale's  carcass  is  picked  bare,  by 
crustaceans    in    particular ;     the    skeleton    is   dissolved 
away  till  only  the  stone-like  ear-bones  are  left.     Of  the 
great  shark  everything  soon  disappears  save  the  teeth. 

(d)  Representative  Fauna. — The  animal  population  of  the 
abysses  includes  representatives  of  most  of  the  classes  of 
animals  from  Protozoa  to  Fishes.     Let  us  run  through  the 
list.     There  are  many  kinds  of  Foraminifera  and  a  few 
Radiolarians    (not  including,  of  course,  the  sunk  shells  of 


THE   HAUNTS  OF   LIFE 

surface  forms 
of  both  these 
types) ;  there 
are  many 
siliceous 

sponges,     but 

no  calcareous 

ones ;      there 

are  sea-ane- 
mones and 

some    related 

corals    and 

very  decora- 
tive Alcyona- 

rians ;  Anne- 
lids and  some 

other '  worms ' 

burrow  in  the 

ooze ;     Echi- 

n  o  d  e  r  m  s 

abound  — 

starfishes, 

brittle  -  stars, 

sea  -  urchins, 

sea  -cucum- 
bers, and 

sea-lil  i  e  s 

swaying       on 

their      stalks 

like  daffodils  FIG  29._Three  Pennatulidg 
with  very  long  stalks. 
I.  Chunella ;  II.  Funicu- 
lina;  III.  Urabellula. 


by   the   lake- 
side ;   Crusta- 


THE  WONDER  OF  LIFE 


ceans  have  a  rich  representation  at  many  levels  of  com- 
plexity, and  there  are  quaint  Sea-Spiders  or  Pycnogonids 
which  are  neither  spiders  nor  crustaceans  ;  most  of  the 
molluscan  types  are  in  abundant  evidence  ;  and  finally 
there  is  a  weird  army  of  voracious  abyssal  fishes. 

Adaptations.  —  A  common  feature  in  the  sedentary 
Deep-Sea  animals  is  the  possession  of  long  stalks  on  which 
the  more  essential  parts  of  the  body  are  raised  high  out 
of  the  treacherous  ooze.  We 
see  this  useful  adaptation  in 
the  surpassingly  beautiful 
Crinoids  which  grow  some- 
times in  great  beds,  in 
Alcyonarians  such  as  Umbel- 
lulas  and  Funiculinas,  and  in 
some  of  the  sponges  like  the 
Glass-Rope-Sponge.  In  some 
of  the  Alcyonarians  the  sup- 
porting stalk  which  bears  the 
colony  of  polyps  on  its  sum- 
mit may  be  over  a  yard  in 
length. 

A  similar  adaptation  is  seen 
in  the  extraordinarily  long 
limbs  which  many  of  the 
Crustaceans  and  Sea-Spiders 
exhibit.  They  illustrate  an 
FIG.  30.—  Deep-Sea  Brittle  extreme  of  lankiness  and  they 

Star  or  Ophiuroid,  Astro-  J 

charis  virgo,  showing  the      may  be  thought  of  as  walking 
onstilte.     In  many  cases  the 


liable  to  breakage—  and      limbs  are  several  times  longer 

the  very    small    central 

disc.    (4/terKoehler.)          than    the    body.     There    can 


THE  HAUNTS  OF  LIFE  91 

be  little  doubt  that  these  elongated  limbs  are  suitable  for 
moving  delicately  on  the  soft  surface.  Some  of  the  Deep- 
Sea  Brittle-stars  show  a  great  reduction  of  the  central  disc 
and  a  great  elongation  of  the  arms  as  compared  with  shallow 
water  forms.  It  may  be  noted  that  the  extraordinary 
elongation  of  limbs  and  the  like  is  quite  incompatible  with 
any  conditions  except  those  of  perfect  calm. 

Many  Deep-Sea  animals  are  very  delicately  built,  with 
bodies  thoroughly  permeable  by  water.  A  delicate  struc- 
ture like  Venus's  Flower  Basket  (Euplectella)  which  is 
shivered  in  a  child's  fingers,  is  admirably  suited  to  great 
depths  where  there  are  tons  of  pressure  on  the  square  inch. 
The  whole  body  is  open  to  the  water  and  the  pressure  is  not 
felt.  For  while  a  hermetically  sealed  glass  vessel  is  crushed 
in  when  it  is  lowered  into  deep  water,  an  open  glass  vessel, 
no  matter  how  delicate,  is  not  affected.  On  the  Challenger 
expedition,  Mr.  J.  Y.  Buchanan  made  an  instructive  experi- 
ment which  has  been  often  cited.  He  took  a  hermetically- 
sealed  empty  glass  cylinder,  wrapped  it  up  in  flannel,  en- 
closed it  in  a  copper  cylinder  with  perforated  ends,  and 
lowered  it  to  2,000  fathoms.  At  a  certain  depth  the  glass 
cylinder  was  shivered  into  snowy  powder,  for  its  walls  could 
not  withstand  the  increasing  outside  pressure  of  the  water. 
The  shivering  took  place  so  suddenly  that  before  water 
could  rush  in  to  fill  the  vacant  space,  one  side  of  the 
copper  cylinder  caved  in.  As  Prof.  Wy ville  Thomson  said, 
an  '  implosion  ',  not  an  explosion,  occurred. 

When  an  abyssal  fish  rising  suddenly  gets  into  a  zone  of 
much  reduced  pressure,  the  gas  in  its  swim-bladder,  which 
had  its  pressure  adjusted  to  the  greater  depth,  expands, 
and  the  fish,  in  spite  of  itself,  is  hurried  to  the  surface, 
'  tumbling  upwards',  as  Professor  Hickson  puts  it.  The 


92  THE  WONDER  OF  LIFE 

transition  is  too  rapid  for  a  readjustment  to  be  effected. 
It  is  well  known  that  Deep-Sea  fishes  brought  up  in  the 
dredge  are  apt  to  suffer  explosion  and  distortion  in  the 
ascent. 

Another  adaptation  that  leaps  to  the  eye  is  the  specializa- 
tion of  tactile  appliances,  as  is  natural  enough  in  a  world  of 
darkness.  There  may  be  antennae  longer  than  the  whole 
body,  groping  a  long  distance  ahead,  so  that  the  animal 
can  feel  its  way  as  a  blind  man  does  with  his  stick.  Many 
of  the  long  legs  of  crustaceans  bear  tactile  bristles  and  many 
of  the  fishes  have  long  slender  barbules  stretching  back- 
wards from  the  chin  or  from  the  fins.  They  are  often  well- 
innervated  and  their  suitability  for  the  conditions  is  evident 
enough. 

An  Extraordinary  Deep -Sea  Cuttlefish. — As  an 
example  of  an  extraordinary  abyssal  type,  we  may  take 
Cirrothauma  murrayi,  one  of  the  captures  of  the  Michael 
Sars  North  Atlantic  Deep-Sea  Expedition  of  1910,  which 
was  carried  out  under  the  auspices  of  the  Norwegian  Govern- 
ment and  the  superintendence  of  the  late  Sir  John  Murray 
and  Dr.  Johan  Hjort.  Three  thousand  metres  of  wire  were 
out  when  this  new  cuttlefish,  which  has  been  carefully  de- 
scribed by  Prof.  Chun,  was  captured,  and  it  is  a  wonder 
that  it  came  up  in  a  condition  to  be  examined.  For  its 
fragility  recalled  that  of  a  Ctenophore,  which  is  saying  a 
good  deal ;  the  body  was  gelatinous  and  semi-transparent ; 
a  delicate  web  united  the  arms,  through  the  whole  length  of 
which  the  nerves  could  be  seen  shining.  The  gelatinous 
body  had  an  exceedingly  faint  violet  colour,  while  the  parts 
round  the  mouth  and  the  basal  portions  of  the  arms  showed 
the  purple  chocolate  colour  which  occurs  in  many  Deep-Sea 
animals.  While  most  cuttlefishes  are  covered  with  chroma- 


FIG.  31. — Deep-sea  Cuttlefish,  Cirrothauma  murrayi.    (After  Chun.) 


THE  HAUNTS   OF   LIFE  93 

tophores,  this  denizen  of  the  great  depths  had  only  one, 
'  a  rhombic  chromatophore  between  the  two  fins  '.  The 
arms  bore  some  normal  suckers,  but  each  had  thirty-six 
others  of  minute  size,  flattened  and  without  sucking  disc, 
and  showing  in  each  case  in  the  long  spindle-shaped  and 
clumsy  stalk  a  curious  structure  which  may  be  a  lumines- 
cent organ  and  reflector. 

The  eyes  are  of  interest,  in  illustration  of — the  subtlety 
of  life.  There  are  Deep-Sea  cuttlefishes  with  small  eyes, 
as  one  might  expect,  but  this  is  the  only  case,  recorded 
as  yet  (1914),  in  which  the  actual  structure  of  the  eye  is 
involved.  For  this  cuttlefish  is  blind  !  The  eye  is  minute, 
without  a  lens,  with  a  very  degenerate  retina  and  optic 
nerve.  Nature  is  economical,  as  we  say  in  metaphor ; 
but  here  she  seems  to  have  been  parsimonious  to  a  degree 
almost  hazardous.  The  degeneration  of  thisCephalopod's 
eye  has  gone  further  than  in  many  blind  vertebrates.  It 
is  adaptive,  apparently,  to  conditions  of  abyssal  darkness ; 
but  surely  it  remains  sensitive  to  the  luminescent  sparkles 
of  its  own  arms  and  the  prey  they  grope  for. 


Problems  of  Deep -Sea  Fauna. 

There  are  many  unsolved  problems  in  the  Deep  Sea, 
and  one  of  the  most  obvious  of  these  is  the  frequent  occur- 
rence of  'phosphorescence'.  It  is  seen  in  animals  of  high  and 
low  degree ;  it  is  exhibited  by  sedentary  animals  and  by 
free  swimmers  ;  it  is  associated  with  a  great  variety  of 
highly  specialized  organs ;  and  these  are  occasionally 
situated  on  most  extraordinary  places — near  the  end  of  the 
tail,  on  the  tip  of  a  long  flexible  rod,  inside  the  mantle- 
cavity  of  a  cuttlefish,  or  inside  the  gill-chamber  of  a  crusta- 


94  THE  WONDER  OF  LIFE 

cean.     It  is  so  common  that  it  surely  has  some  significance. 

Perhaps  it  has  different  meanings  in  different  animals, 
and  there  is  no  lack  of  suggestions.  May  it  be  sometimes 
a  lure,  attracting  victims,  who  come  like  moths  to  the 
candle  ?  Is  it  sometimes  an  advertisement  on  the  part  of 
unpalatable  creatures,  warning  off  intruders  and  molesters, 
as  the  rattlesnake  does  with  its  rattle  ?  Does  it  some- 
times serve  as  a  lantern,  guiding  the  active  animal  to  its 
prey  ?  Of  course  that  would  not  apply  to  cases  where 
the  light  is  at  the  hind  end !  Does  it  serve  in  some  cases 
as  a  '  recognition  mark ',  enabling  those  of  the  same  kin 
to  know  one  another  ?  In  some  fishes  the  disposition  of 
the  luminescent  organs  on  the  body  is  different  in  the  two 
sexes.  But  phosphorescence,  as  it  is  called,  remains  an 
unsolved  problem. 

Another  difficulty  is  raised  by  the  fact  that  there  is  so 
much  colour  in  Deep-Sea  animals.  What  can  be  the  use  of 
that  in  an  abode  of  darkness  ?  There  are  many  reds,  e.g. 
in  Crustaceans  and  Anemones  ;  there  are  shades  of  orange 
and  yellow ;  there  are  some  instances  of  beautiful  blue  ; 
there  is  almost  no  green.  It  is  noteworthy  that  there  is 
very  little  in  the  way  of  spots  or  stripes,  most  of  the  animals 
being  all  one  colour.  It  is  probable  enough  that  there  is 
no  utilitarian  interpretation  of  these  Deep -Sea  colours, 
which  may  be  simple  by-effects  of  useful  structures  and 
functions.  It  may  be  that  the  Deep-Sea  colours  are  like 
those  in  withering  leaves — without  utility  in  themselves. 

The  autumn  colouring  of  withering  leaves  is  largely  due 
to  the  ebbing  vitality,  just  as  floral  colouring  is  largely  due 
to  intense  vitality.  Decomposition  products  in  the  former, 
waste  products  in  the  latter  may  not  be  chemically  far 
apart.  But  while  the  pigmentation  of  the  flowers  is  turned 


THE  HAUNTS  OF  LIFE 


95 


to  good  account  as  a  means  of  attracting  insects,  no  one 
has  ever  suggested  any  utility  in  the  gorgeous  colours  of 
the  autumn  woods.  They  are  the  outcome  of  very  im- 
portant physiological  processes,  but  they  are  not  them- 
selves of  use ;  and  the  same  is  probably  true  of  the  reds 
and  other  bright  hues  of  many  abyssal  animals. 

Another  general  problem — the  most  general  of  all — is 
raised  by  the  fact  that  many  Deep-Sea  animals  are  quite 
closely  related  to  shore  animals,  with  essentially  the 


FIG.  32. — Two  Deep-Sea  Fishes. 


L,  Luminous  organ. 


same  functions  discharged  by  essentially  the  same  organs, 
and  yet  under  such  different  conditions  of  temperature  and 
pressure.  Processes  of  digestive  fermentation,  for  in- 
stance, which  go  on  in  shore  animals  in  the  warmth  of 
the  Tropics,  are  also  going  on  on  the  floor  of  the  Deep  Sea 
at  a  temperature  near  the  freezing-point  of  fresh  water. 
We  know  that  warmth  up  to  a  certain  limit  hastens  growth  ; 
we  should  like  to  have  facts  in  regard  to  the  rate  of 
growth  in  the  eternal  winter  of  the  Deep  Sea. 


96  THE  WONDER   OF  LIFE 

In  reporting  on  the  free- living  marine  Nematodes 
collected  at  Cape  Royds  on  the  Shackleton  Expedition, 
Mr.  N.  A.  Cobb  refers  to  the  same  problem  of  vigorous  life 
in  extraordinary  conditions.  Hundreds  of  specimens, 
males,  females,  and  young,  were  taken  from  a  mere  thimble- 
ful of  the  dredgings.  They  seem  to  be  rather  smaller 
than  species  in  warmer  seas,  but  they  do  not  seem  to  be 
less  prolific.  '  It  is  hardly  conceivable  that  the  body 
temperature  of  the  marine  polar  species  is  higher  than  that 
of  the  water  in  which  they  live,  namely,  near  the  freezing 
point  of  fresh  water,  and  yet,  in  spite  of  the  freezing  tem- 
perature, and  the  long  polar  night,  nematode  protoplasm 
seems  to  glide  on  through  its  mitosis  dance  to  much  the 
same  purpose  as  if  bathed  in  equatorial  light  and  ensconced 
in  the  warm  pools  of  tropical  reefs.' 

Of  detailed  problems  there  is  a  long  list,  but  we  must 
be  content  with  one  illustration.  It  concerns  the  eyes 
of  fishes.  When  we  take  a  series  of  fishes  from  various 
depths,  starting  with  the  shore,  we  find  that  some  of  those 
from  moderate  depths  (300-600  fathoms)  have  very  large 
eyes,  and  it  seems  reasonable  to  interpret  this  as  an  adapta- 
tion to  the  failing  light.  We  also  find  that  some  of  those 
from  great  depths,  of  over  1,000  fathoms,  have  very  small 
eyes,  and  it  seems  reasonable  to  associate  this  with  the 
darkness.  A  useless  eye  will  tend  to  dwindle,  for  the 
individuals  with  least  of  it  will  get  on  best.  But  the  difficulty 
is  that,  along  with  the  abyssal  fishes  with  very  small  eyes, 
there  are  others  which  have  very  large  ones.  It  is  difficult 
to  see  how  both  conditions  can  be  adaptive.  Two  sugges- 
tions have  been  made :  that  those  abyssal  fishes  with 
large  eyes  are  relatively  newcomers,  in  which  the 
dwindling  process  has  not  begun,  or  that  they  are 


THE  HAUNTS   OF  LIFE  97 

adapted  to  make  use  of  the  gleams  of  phosphorescent 
light. 

The  Question  of  Origin. — As  to  the  origin  of  the 
Deep-Sea  fauna,  the  evidence  points  to  the  conclusion  that 
the  abysses  have  been  persistently  colonized  age  after  age 
by  migrants  from  the  shore  and  from  the  '  Mud-Line'. 
There  is  a  marked  resemblance  between  certain  representa- 
tives of  the  Deep-Sea  fauna  in  a  given  region  and  representa- 
tives of  an  adjacent  shore  fauna.  Quite  a  number  of  Deep- 
Sea  animals  have  affinities  with  Polar  animals.  It  is  un- 
likely that  the  Deep-Sea  fauna  was  established  long  before 
the  Cretaceous  times,  and  perhaps  the  cooling  of  the  Poles 
and  the  setting  up  of  a  bottom-movement  equatorwards 
of  cold  water  rich  in  oxygen  was  one  of  the  conditions  of 
the  abysses  becoming  a  home  of  life.  The  rarity  of  primi- 
tive types  in  the  Deep  Sea  shows  that  we  cannot  regard 
the  fauna  as  made  up  of  relics  of  very  ancient  days. 

Professor  Johannes  Walther  calls  attention  to  the  signifi- 
cant fact  that  no  Palaeozoic  types  occur  in  the  present  Deep- 
Sea  fauna.  Archaic  forms  like  Lingula  (lamp-shell),  Limu- 
lus  (king-crab),  Nautilus,  Pleurotomaria,  Mytilus,  Serpula, 
and  Astropecten  are  littoral,  not  abyssal.  The  present-day 
Deep-Sea  animals  do  not  date  back  further  than  the 
Triassic  period,  and  some  of  them  are  closely  related  to 
Cretaceous  types.  Walther  works  on  to  the  interesting 
suggestion  that  the  enormous  elevation-movements  which 
led  to  the  Hercynian  range  in  Europe,  the  Appalachians  in 
America,  and  Sudanese  mountains  in  Africa  were  associ- 
ated with  complementary  depressions  which  formed  the 
great  abysses  of  the  ocean. 

The  Wonder  of  the  Deep  Sea. — In  one  of  his  last 
writings  Herbert  Spencer  complained  of  the  unreflective 


98  THE  WONDER  OF  LIFE 

mood  among  cultured  and  uncultured  alike,  '  which  does 
not  perceive  with  what  mysteries  we  are  surrounded'. 
'  By  those  who  know  much',  he  said,  '  more  than  by  those 
who  know  little,  is  there  felt  the  need  for  explanation'. 
'  What ',  for  instance,  '  must  one  say  of  the  life,  minute, 
multitudinous,  degraded,  which,  covering  the  ocean  floor, 
occupies  by  far  the  larger  part  of  the  earth's  area ;  and 
which  yet,  growing  and  decaying  in  utter  darkness,  pre- 
sents hundreds  of  species  of  a  single  type  '  ?  This  raises 
the  question  of  the  deeper  significance  of  the  abyssal  fauna. 

In  the  first  place,  it  seems  useful  to  remind  ourselves 
that  a  knowledge  of  the  Deep  Sea  has  cut  into  human  life  ; 
it  has  been  of  value  to  mankind,  practically,  in  connexion 
with  laying  cables  (and  that  has  meant  much) ;  intellectu- 
ally, for  it  has  been  an  exercise-ground  for  the  scientific 
investigator  ;  emotionally,  for  there  is  perhaps  no  more 
striking  modern  gift  to  the  imagination  than  the  picture 
which  explorers  have  given  of  the  eerie,  cold,  dark,  calm, 
silent,  plantless,  monotonous,  but  thickly  peopled  world  of 
the  Deep  Sea. 

Yet  this  cannot  be  its  full  meaning.  So  perhaps  we  get 
nearer  the  heart  of  the  problem  when  we  recognize  the 
simple  fact  that  the  Deep  Sea  is  an  integral  part  of  the 
whole.  Just  as  the  making  of  the  great  '  deeps  '  was  corre- 
lated with  the  raising  of  great  mountains,  so  the  abyssal 
fauna  is  wrapped  up  with  the  whole  vital  economy  of  the 
Earth.  For  it  is  the  overflow  basin  of  the  great  fountain  of 
life  whose  arch  is  sunlit.  It  is  necessary  to  the  wholesome- 
ness  of  the  ocean.  It  is  the  universal  clearing-house. 

And  perhaps  we  may  go  a  little  deeper  still,  for  when  we 
recognize  that  insurgent  life  which  will  not  be  gainsaid  has 
conquered  the  abyssal  desert,  that  this  by-way  is  full  of 


THE  HAUNTS  OF  LIFE  99 

beauty  not  surpassed  elsewhere,  and  especially  that  there 
is  here  the  same  order  and  rationality  and  pervasive  pur- 
posiveness  that  we  find  elsewhere,  then  we  begin  to  perceive 
that  the  life  of  the  Deep  Sea  is  part  of  the  embodiment  of 
what  appears  to  us  as  a  great  thought.  To  the  question 
of  significance,  which  forces  us  far  beyond  Science,  William 
Watson  has  given  us  the  poet's  answer  : — 

Nay,  what  is  nature's 
Self,  but  an  endless 
Strife  towards  music, 
Euphony,  rhyme  ? 

Trees  in  their  blooming, 
Tides  in  their  flowing, 
Stars  in  their  circling, 
Tremble  with  song. 

God  on  His  throne  is 
Eldest  of  poets, 
Unto  His  measures 
Moveth  the  whole. 

IV.     THE  FRESHWATER  FAUNA 

The  systematic  study  of  the  freshwater  fauna  began 
before  that  of  the  shore  or  of  the  deep  sea,  for  men  like 
Reaumur  (1683-1757),  Rosel  von  Rosenhof  (1705-1759), 
and  Trembley  (1700-1784),  who  had  the  joy  of  discovering 
and  naming  some  of  the  commonest  inhabitants  of  our 
lakes  and  ponds,  laid  broad  and  deep  foundations  before 
there  was  much  in  the  way  of  marine  zoology.  But  when 
the  fauna  of  the  sea  began  to  be  systematically  studied, 
attention  was  in  great  measure  charmed  away  from  the 
freshwaters,  and  it  is  only  in  the  last  quarter  of  a  century 
or  so  that  this  haunt  of  life  has  begun  again  to  receive  its 
due  share  of  investigation. 


ioo  THE  WONDER  OF   LIFE 

It  is  said  that  the  freshwaters  occupy  about  1,800,000 
square  miles,  but  that  is  a  small  fraction  of  the  total  of 
about  197,000,000  for  the  earth's  surface.  In  some 
countries,  however,  the  freshwater  area  is  very  considerable; 
thus  in  Finland  it  is  estimated  at  about  13  per  cent.  The 
relative  smallness  of  the  freshwaters  is  made  up  for  in  a  way 
by  the  scattered  distribution  and  the  correlated  great 
diversity  in  character.  How  many  different  forms  there 
are,  with  no  unity  except  in  the  word  fresh — the  large 
deep  lake  with  storms  like  those  at  sea,  the  mountain  tarn 
with  its  dark  mysterious  surface,  the  shallow  pond  with  a 
population  in  many  respects  different  from  that  of  the 
lake,  the  ephemeral  pool,  the  permanent  well,  the  swamp, 
the  ditch,  the  brook  and  the  river.  Nor  do  these  exhaust 
the  list;  thus  in  a  detailed  German  classification  we  find 
a  special  subdivision  for  water-pipe  fauna.  It  is  recorded 
that  before  the  improvement  of  the  filtering  in  connexion 
with  the  water-supply  of  a  large  town  on  the  Continent, 
no  fewer  than  sixty-one  animals  were  obtained  from  the 
pipes — including  eels,  sticklebacks,  water-snails,  insect 
larvae,  worms,  and  the  freshwater  sponge.  For  practical 
purposes,  it  may  be  noted,  large  intruders  are  often  unim- 
portant. The  serious  thing  is  when  some  fungus,  like 
Crenothrix,  takes  up  its  abode  in  the  pipes. 

Of  the  various  forms  which  accumulations  of  fresh  water 
may  assume,  the  lake  or  loch  is  most  important.  It  is 
distinguished  from  the  pond  not  so  much  by  its  size  as  by 
depth,  which  reaches  a  maximum  in  Lake  Baikal,  with  its 
760  fathoms.  In  typical  lakes  we  can  readily  distinguish 
(1)  the  relatively  shallow  shore-area,  (2)  the  open  water, 
and  (3)  the  dark  quiet  dreary  plain  at  the  foot  of  the  steep 
slope  or  talus  which  runs  from  the  shore-shelf  downwards. 


THE  HAUNTS  OF  LIFE  101 

Thus  in  true  lakes,  as  in  the  sea,  we  have  to  distinguish 
a  littoral,  a  pelagic,  and  an  abyssal  fauna. 

Physical  Conditions. — The  physical  conditions  of 
freshwater  basins  are  of  course  very  diverse,  and  they 
determine  noteworthy  differences  in  the  fauna  and  flora. 
Thus  it  is  well  known  that  certain  organisms,  such  as 
the  stonewort  Chara,  and  the  freshwater  crayfish,  Astacus, 
require  that  there  be  a  relatively  large  percentage  of 
carbonate  of  lime  in  the  water,  while  others,  like  the  fresh- 
water mussels,  do  not  thrive  if  there  is. 

Concerning  temperature,  it  is  obvious  that  in  summer 
that  of  the  surface  is  higher,  while  in  winter,  especially 
when  there  is  ice,  that  of  the  bottom  is  higher.  Averages 
on  the  surface  for  the  four  seasons  read  like  this  :  Spring 
6-7°  C.,  Summer  17-8°  C.,  Autumn  11-9°  C.,  Winter  3'9°  C. 
In  summer,  or  indeed  for  about  280  days  in  the  year,  when 
the  warmer  water  is  at  the  top,  there  is  a  decrease  down 
to  4°  C.,  the  temperature  of  water  at  its  greatest  density, 
but  the  decrease  downwards  is  not  uniform — there  being 
a  strange  leap  between  5  and  10  fathoms.  In  winter,  for 
about  85  days  in  the  year,  when  the  colder  water  is  at  the 
top,  there  is  an  increase  downwards  until  4°  C.  is  reached. 
For  a  short  time  twice  a  year,  the  temperature  is  practically 
uniform  throughout.  It  should  also  be  remembered 
that  for  each  5  fathoms  there  is  almost  an  additional 
atmosphere  of  pressure. 

The  degree  of  illumination  is  of  vital  importance  as 
regards  the  distribution  of  both  plants  and  animals,  and 
the  depth  to  which  light  can  penetrate  varies  considerably, 
especially  with  the  purity  and  colour  of  the  water.  The 
red  rays  are  lost  first,  the  violet  rays  go  deepest.  A 
common  average  result  with  a  white  plate  is  that  it  ceases 


102  THE  WONDER  OF  LIFE 

to  be  visible  at  about  3  fathoms,  but  we  have  to  multiply 
this  by  two  since  the  light  has  to  travel  up  again  from  the 
plate,  so  that  a  common  average  for  light-penetration  is  6 
fathoms.  In  very  clear  water,  as  in  the  Lake  of  Constance 
in  winter,  the  figure  may  rise  to  over  12  fathoms.  And 
this  must  be  further  extended  if  we  take  the  chemical  rays 
into  account,  for  silver  chloride  paper  is  affected  at  55 
fathoms  and  silver  bromide  paper  at  over  90  fathoms. 

The  diverse  coloration  of  freshwater  basins  raises  a 
number  of  interesting  and  difficult  questions.  Chemically 
pure  water  is  said  to  have  an  azure  blue  colour.  The 
addition  of  numberless  impalpable  dust  particles  pro- 
duces a  yellowish  tint,  which  along  with  the  primitive  blue 
gives  green.  Thus  we  have  to  thank  the  dust  for  the 
colour  of  the  lake  as  well  as  of  the  clouds  overhead.  But 
the  green  is  often  in  part  due  to  millions  of  unicellular 
Algae.  A  tawny  yellow,  familiar  in  the  rivers  of  the  Scottish 
Highlands,  may  be  produced  by  abundance  of  dissolved 
organic  matter — humic  acid  and  the  like.  A  most  remark- 
able iridescence  of  water  is  sometimes  seen  when  the  sur- 
face is  covered  with  millions  of  the  translucent  moulted 
cuticles  of  water-fleas,  but  the  splendour  of  this  has  to  be 
seen  to  be  believed.  The  practical  importance  of  the  colour 
of  the  water  is  in  connexion  with  its  penetrability  by  light ; 
the  blue  water  is  most  penetrable,  the  green  less,  the  yellow 
still  less. 

Various  Lacustrine  Regions. — The  littoral  or  shore 
area  of  the  lake  may  be  broad  or  narrow  according  to  the 
configuration  of  the  lake.  Like  the  corresponding  sea- 
shore area,  it  is  subject  to  great  vicissitudes — diurnal  and 
seasonal,  it  is  often  full  of  movement,  it  is  strongly  illumined, 
it  has  a  rich  vegetation,  and  it  is  often  crowded  with 


THE  HAUNTS  OF  LIFE  103 

animals.  It  is  marked  by  such  plants  as  the  stonewort 
(Cham),  mare's  tail  (Hippuris),  pond- weeds  (Potamogeton), 
duckweed  (Lemna),  water-lilies,  Ranunculus  lingua,  Alisma 
pkmtago,  bog-bean,  and  so  forth.  Some  show  interesting 
adaptations  of  mobility  and  elasticity  suited  to  the  turbu- 
lence of  the  shore. 

As  to  the  animal  life,  it  is  varied.  By  the  shore  there 
may  be  nests  of  gulls  and  wild  duck,  of  coot  and  moorhen. 
The  shallows  are  the  home  of  frogs  and  sticklebacks,  of  carp 
and  miller's  thumb  (Cottus  gobio).  The  freshwater  mussels 
plough  their  leisurely  way  along  the  mud  ;  the  water-snails 
glide  back  downwards  along  the  surface-film.  The  water- 
spider  weaves  her  diving-bell  nest,  and  beautifully  coloured 
water-mites  rush  to  and  fro.  There  are  countless  Crus- 
taceans, like  Daphnia  and  Sida,  Diaptomus  and  Cyclops  ; 
fixed  Rotifers  like  Floscularia  and  Melicerta — miracles  of 
beauty ;  some  equally  fascinating  freshwater  Polyzoa  ; 
simple  Planarian  worms  wafting  themselves  along  the  water 
weed  by  their  unseen  cilia  ;  besides  Hydra  and  freshwater 
sponges  and  many  Protozoa.  We  have  given  samples 
enough  to  show  that  the  shore  of  the  lake  has  a  very 
representative  fauna. 

The  second  great  region  in  lakes  is  the  open  water, 
tenanted  by  a  pelagic  or  limnial  fauna  and  flora.  The 
vegetation  is  represented  by  numerous  Alga3,  by  duck- 
weed and  Ceratophyllum,  by  the  beautiful  rootless  Bladder- 
wort  (Utricularia)  with  its  neat  traps  for  water-fleas. 
Some  show  gas  vesicles  which  ensure  floating.  As  to 
animals,  there  are  Infusorians  (e.g.  species  of  Ceratium 
and  Peridinium),  numerous  Rotifers,  legions  of  water- 
fleas,  not  a  few  water-mites  (such  as  Atax  crassipes  and 
Curvipes  rotundus),  a  few  insect  larvae,  e.g.  of  Corethra 


104  THE  WONDER  OF  LIFE 

plumicornis,  and  also  the  larval  stages  of  some  shore  forms, 
e.g.  of  the  bivalve  Dreissensia.  In  the  transparency,  the 
delicacy  of  build,  and  the  occasional  presence  of  long  pro- 
cesses— believed  to  be  useful  in  drifting — we  see  adaptations 
to  the  open  water  life. 

The  success  of  a  lake  depends  to  a  large  extent  upon 
the  open  water  population,  and  waxes  and  wanes  with  its 
vicissitudes.  A  few  forms  are  almost  uniformly  abundant 
all  the  year  round,  but  the  majority  show  a  marked  periodi- 
city. Thus  the  Rotifer  Synchceta  has  its  climax  in  spring, 
and  there  may  be  about  three  millions  to  the  square  yard 
in  April.  The  well-known  Diatom,  Melosira  varians,  has 
two  maxima  in  the  year,  one  in  July  and  one  in  October, 
and  may  attain  in  the  last-named  month  to  the  astonishing 
abundance  of  about  7,000  millions  to  the  square  yard. 
The  slimy  Alga,  Clathrocystis  aeruginosa,  has  its  climax 
about  August,  with  about  500  millions  to  the  square  yard. 
Others,  again,  have  their  maximum  in  winter,  such  as  the 
Copepod  Crustacean,  Diaptomus  gracilis,  whose  propor- 
tionate representation  for  the  four  seasons  is  indicated  by 
the  figures— 760  for  April,  7,900  for  August,  31,160  for 
September,  and  121,290  for  January.  The  broad  fact  to 
be  realized  is  that  the  upper  layers  of  the  open  water  are 
the  chief  productive  areas,  where  the  Algae  utilize  the 
energy  of  the  sunlight  to  build  up  the  carbon-compounds 
which  form  the  fundamental  food  supply  of  all  the  lacustrine 
population. 

The  third  great  region  is  that  of  the  greater  depths  of 
the  lake,  a  region  of  uniformity,  where  there  is  neither 
day  nor  night,  where  the  temperature  is  low  and  relatively 
uniform,  where  the  pressure  is  very  great,  where  there  are 
no  movements  apart  from  life,  and  where  there  is  usually 


FIG.  33. — Three  closely  related  species  of  Cyclops.  A.  Cyclops 
distinctus.  B.  Cyclops  fuscus.  C.  Cyclops  albidus,  probably 
a  hybrid  between  the  other  two.  All  the  specimens  shown 
are  females.  The  median  eye  is  well  seen.  (After  Neubaur.) 
1.  Antenna.  2.  Antennule.  3.  Egg-sac.  4.  Caudal  filaments. 


104 


Tttfe  WONDER  OF  LIFE 


plumicomts,  ai 
e.g.  of  the  biv 
delicacy  <>i  *;>** 
ceases  —  bali*** 
to  the  «>«•.  w 
The  >«.'^--a* 
the  or*«  - 


t&*r  Urv«i  *<*g*s  *rf  some  shore  forms, 
rcMtewi*,     In  fcbc  transparency.  the 

:&?  :•*••'-«**  ;•<**«.<  presence  of  long  pro- 
aptations 


to  a  large  extent  upon 
axes  and  wanes  with  its 
ost  uniformly  abundant 
show  a  marked  periodi- 
has  its  climax  in  spring, 
hons  to  the  square  yard 
i.  Mdosira  varians,  has 


.A     .2qoby3  ^o  sabsqa 
.aubidb  gqoIoyD  -D 
nworfe  ansmbsqe  aHl  IIA    .owl 
ia\\K)     .nase  Haw  ai 


Oopep 


the  figures--  -'&>  , 

be  re*.l!3*»Ji 

TJM      ;  ,-  ; 

energy  uf  it>>  wtak^' 

which  f  onii 

population. 

The  third  great  n$. 
the  lake,  a  region  «f  vfli 
day  nor  night,  where  cfcc 
uniform,  where  the  pnaeu 
no  movements  apart 


-  ,a      ,8yl?ndaib 
isHlo  sHj.nMvd^  gn®^ 
ys  niiibani  arfT      .»limpf  STB 
.s^nnaJriA  .S    .finnainA  ':.1 
Lrd. 

«t,  «»eh  as  the 

•  --'-^c  prupor- 

•'  iicated  by 

u»t,  31,160  for 

•    broan  fact  to 

-  'i»en  water  are 

?.ie  Algae  utilize  the 

?     ca  :    n  compounds 

-  •  y  of  all  the  lacustrine 

le  greater  depths  of 
y,  where  there  is  neither 
»ture  is  low  and  relatively 


THE  HAUNTS  OF  LIFE  105 

much  mud.  It  is  the  least  populous  region.  Since  it  is 
dark,  there  are  practically  no  plants  except  Bacteria  and 
the  like.  The  animal  population  includes  Amoebae  and 
their  relatives  (e.g.  species  of  Difflugia  and  Arcella), 
Infusorians  like  Stentor  and  Vorticella,  a  deep-water  reddish 
Hydra,  simple  Turbellarian  and  Nematode  worms,  others 
of  higher  degree  like  Nais,  some  species  of  Fredericella 
and  Paludicella  among  Polyzoa,  a  number  of  Crustaceans 
(e.g.  blind  species  of  Cyclops  and  Asellus),  some  insect 
larvae,  e.g.  of  the  harlequin  fly,  a  few  water-mites  like 
Hygrobates,  a  few  molluscs  like  the  bivalve  Pisidium 
Jioferi  and  the  Gastropod  Limncea  abyssicola,  and  finally 
a  few  fishes  like  the  giant  Silurus  and  its  small  counterpart, 
the  burbot  (Lota  vulgaris),  which  is  one  of  the  hosts  of  the 
young  stages  of  the  formidable  human  tapeworm  (Bothrio- 
cephalus  lotus),  thus  linking  up  the  dark  depths  of  the  lake 
into  connexion  with  human  life. 

In  regard  to  other  freshwaters,  such  as  ponds  and  rivers, 
it  must  suffice  to  say  that  each  has  its  distinctive  fauna, 
and  that  the  population  in  rivers  is  much  less  abundant 
than  elsewhere.  In  the  actual  current  of  the  Rhine, 
Lauterborn  found  only  twenty  Rotifers,  two  Crustaceans, 
nine  Protozoa,  and  two  Diatoms ;  but  of  course  this  number 
is  greatly  increased  when  we  take  account  of  the  creatures 
— e.g.  larval  insects — that  creep  about  on  the  stones  and 
among  the  weed.  Wherever  there  is  stagnancy,  e.g.  in 
the  pools  of  the  overflow  bed,  we  find  much  the  same 
fauna  as  in  ponds.  As  to  ponds,  while  there  are  a  few 
forms,  e.g.  Leptodora  hyalina,  which  occur  both  in  ponds 
and  lakes,  the  fauna  of  the  shallow  pond  is  usually  quite 
different  from  that  of  a  true  lake.  Thus  no  one  expects  to 
find  a  Crustacean  like  Byotrephes  longimanus  in  a  pond. 


io6  THE  WONDER  OF  LIFE 

Inter -Relations. — There  are  many  good  instances 
among  freshwater  animals  of  the  way  in  which  the  life  of 
one  creature  becomes  wrapped  up  with  that  of  another. 
We  shall  afterwards  refer  to  the  extraordinary  fact  that 
the  continuance  of  the  race  of  freshwater  mussels  depends 
on  the  presence  of  minnows  and  other  small  fishes,  while 
on  the  other  hand,  the  continuance  of  the  freshwater  fish 
known  as  the  bitterling  (Rhodeus  amarus)  depends  on  the 
presence  of  freshwater  mussels.  The  young  stages  of  the 
liver-fluke  of  the  sheep  are  spent  within  the  small  fresh- 
water snail  (Lymnceus  truncatulus),  and  the  larvae  of  the 
formidable  guinea-worm  of  man  are  found  inside  certain 
species  of  water-flea  or  Cyclops.  Some  tropical  freshwater 
fishes  feed  greedily  on  the  aquatic  larvae  of  mosquitoes  and 
thus  help  to  lessen  malaria  which  is  due  to  a  microscopic 
animal  temporarily  parasitic  in  the  insects.  There  are 
endless  nutritive  chains  of  great  practical  importance. 
Thus  the  voracious  cormorants  so  often  shot  down  on  the 
shores  of  the  estuary,  where  they  certainly  engulf  many 
fishes,  are  not  to  be  dismissed  so  summarily,  for  in  certain 
localities  they  keep  down  the  eels  and  crabs  which  destroy 
the  fry  of  valuable  species.  Some  freshwater  fishes  feed 
on  crustaceans  and  insect-larvae,  which  feed  on  minute 
organisms,  which,  again,  depend  on  decaying  organic 
matter.  The  insectivorous  bladderwort  (Utricularia) 
catches  small  animals  in  its  neat  traps  and  these  are  said 
to  be  utilized  by  the  water-spider.  As  we  shall  see,  some 
caddis- worms  spread  nets  for  the  '  dwarf -plankton,'  and 
the  green  freshwater  Hydra  owes  its  colour  and  its  success 
to  having  entered  into  partnership  with  very  minute 
Algae  which  live  within  the  cells  of  its  inner  or  endodermic 
layer. 


THE  HAUNTS  OF  LIFE  107 

Adaptations. — Many  freshwater  animals  run  the  risk 
of  being  periodically  dried  up,  and  there  is  a  series  of 
remarkable  adaptations  to  meet  this  vicissitude.  Many 
are  able  to  survive  prolonged  desiccation.  They  are 
masters  of  the  art  of  '  lying  low  and  saying  nothing ',  as 
Brer  Rabbit  phrased  it.  The  capacity  is  illustrated  by 
some  Protozoa,  Nematodes,  Rotifers,  Bear-Animalcules, 
Entomostracan  Crustaceans,  and  Mites,  but  in  some  cases 
what  survives  is  not  the  animal  itself  but  an  enclosed  egg 
or  germ. 

Writing  in  the  Annals  and  Magazine  of  Natural  History 
in  1898,  Mr.  Atkinson  noted  that  forty  years  before  he  had 
taken  some  samples  of  mud  from  the  ancient  pool  of  Gihon, 
outside  the  Jaffa  Gate  of  Jerusalem,  which  at  that  time 
contained  water  for  only  two  months  of  the  year.  The 
dry  mud  was  sent  to  England  and  moistened,  with  the 
result  that  Dr.  Baird  found  in  the  culture  six  new  species 
of  living  Entomostraca  or  water-fleas.  For  eight  years  in 
succession,  at  the  Leeds  Philosophical  Society's  Museum, 
the  mud  was  dried  up  in  summer  and  moistened  again  in 
spring,  and  its  tenants  still  persisted.  Not  that  any  one 
individual  was  known  to  persist,  but  multiplication  in 
summer  always  provided  individuals  or  resting  eggs  to 
carry  on  the  torch  for  another  period.  In  one  case,  a  small 
sample  was  left  dry  in  a  pill  box  for  nine  years,  and  then 
moistened,  with  the  result  that  in  a  fortnight  a  single 
specimen  of  Estheria  gihoni  made  its  appearance.  Here 
the  torch  was  kept  burning,  either  by  an  individual  or  more 
probably  by  a  resting  egg,  throughout  the  desiccation  of 
nine  years.  In  another  case,  the  alternation  of  drought 
and  moisture  was  kept  up  artificially  for  twenty-four  years, 
with  unvarying  success  as  regarded  persistence  of  vitality. 


io8  THE  WONDER  OF  LIFE 

It  is  well  known  that  specimens  of  the  brine-shrimp 
(Artemia)  can  often  be  got  by  keeping  a  solution  of  Tidman's 
Sea-Salt  for  some  days  till  the  desiccated  germs  hatch  out. 

Belonging  to  another  series  are  the  adaptations  which 
enable  freshwater  animals  to  meet  the  winter,  which  in 
northern  countries  sets  a  spell  on  many  forms  of  life.  It 
sends  many  to  sleep,  like  the  frog  in  the  mud  by  the  pond 
side — mouth  shut,  nostrils  shut,  eyes  shut,  breathing  by 
its  skin  like  a  worm,  and  with  its  heart  beating  ever  so 
feebly.  It  sends  others  to  the  deeper  sleep  of  death,  for 
just  as  winter  prunes  the  trees,  so  it  sifts  the  fauna  of  the 
pond.  There  is  severe  elimination,  and  it  is  therefore 
very  interesting  to  notice  the  '  winter- eggs  '  of  water-fleas 
and  Rotifers  which  are  able  to  withstand  great  severities 
of  temperature,  and  the  strange  '  statoblasts  '  or  resistent 
germs  of  Polyzoa,  and  similar  adaptations  for  surviving 
difficulties  by  a  Fabian  policy  of  waiting.  A  good  example 
is  the  freshwater  sponge,  which  spreads  exuberantly  over 
stones  and  submerged  roots  in  the  summer,  but  soon  feels 
the  pinch  in  autumn.  The  body  of  the  sponge  dies  away, 
and  rots  away,  but  in  the  skeletal  framework,  which 
cannot  rot,  clumps  of  cells  are  formed,  buttressed  round 
by  capstan-like  flinty  spicules,  and  these  gemmuks,  as  they 
are  called,  persist  as  foci  of  life  while  the  parental  corpse 
disintegrates.  When  the  spring  comes  and  the  rivers  are 
in  flood  after  the  melting  of  the  snow,  the  sponge  skeleton 
is  broken  and  the  gemmules  are  carried  hither  and  thither, 
many,  perhaps  most,  to  destruction,  a  few  to  find  a  harbour 
in  suitable  crevices  where  they  may  proceed  to  develop 
into  early  summer  sponges. 

In  times  of  severe  frost  many  animals  seek  safety  in  the 
mud — a  refuge  from  being  imprisoned  in  the  ice.  There 


FIG.  34. — Magnification  of  a  piece  of  fine  '  Miiller's  gauze '  used  in  tow-netting,  showing 
the  organisms  of  the  dwarf  plankton  or  '  Nannoplankton,'  which  are  minute  enough 
to  pass  through  the  invisible  pores  of  the  cloth.  (After  Lohmann.) 


THE  HAUNTS  OF  LIFE  109 

is  undoubtedly  severe  elimination,  but  there  are  some 
tough  creatures  which  do  not  necessarily  die  even  when 
encased  in  ice.  Provided  that  they  can  form  small  cavities 
around  themselves,  they  may  last  till  the  thaw  comes  ; 
thus  a  leech  has  been  known  to  survive  forty- eight  hours 
in  a  block  of  ice.  The  worst  case  is  when  the  ice  is  thick 
on  a  shallow  pond,  for  then  there  is  risk  of  suffocation  ; 
oxygen  becomes  scarce ;  sulphuretted  hydrogen  and 
ammonia  accumulate ;  the  fishes  come  eagerly  to  holes  in 
the  ice ;  and  there  is  often  great  mortality.  We  are 
impressed,  however,  by  life's  toughness  as  well  as  by  its 
fragility ;  thus  the  water-snail,  Limnceus  stagnalis,  may 
be  seen  creeping  quite  actively  on  the  under  surface  of  the 
ice.  Leeches  and  eels  are  also  notable  for  their  powers 
of  resistance.  We  are  familiar  with  the  contrast  between 
the  crowded  and  busy  life  of  the  pond  and  loch  in  summer 
and  the  clear  deserted  appearance  in  winter,  but  the  fact  is 
that  the  water  is  seldom  so  empty  as  it  looks.  There  is 
plentiful  life  in  some  of  the  Alpine  lakes  which  are  frozen 
most  of  the  year ;  and  in  the  depth  of  winter  in  Britain 
and  similar  countries  there  may  be  abundant  representa- 
tion of  '  water-fleas',  rotifers,  bear-animalcules,  infusorians, 
amoebae,  and  other  small  animals. 

Vital  Economy  of  the  Freshwaters. — The  population 
of  a  freshwater  basin  may  be  divided  into  producers, 
consumers,  and  middlemen.  The  raw  materials  consist  of 
air,  water,  and  salts,  which  the  producers,  the  green  plants, 
work  up,  with  the  help  of  the  sunlight,  into  complex 
carbon  compounds.  These  are  utilized  by  the  consumers, 
the  animals,  who  dissipate  the  stores  of  energy  which  the 
plants  have  accumulated.  The  middlemen  are  in  great 
part  the  Bacteria,  which  often  make  vegetable  products 


no  THE  WONDER  OF  LIFE 

more  available  for  animal  use,  and  also  break  up  the 
dead  bodies  of  animals  into  material  that  can  be  used  by 
plants  as  food. 

Besides  Bacteria  there  are  other  extremely  minute 
forms  of  life  which  play  an  important  part  in  the  vital 
economy  of  the  freshwaters.  Such  are  the  Desmids, 
Diatoms,  Phyto-flagellates,  and  Zoo-flagellates — which 
Prof.  Lohmann  of  Kiel  sums  up  in  the  word  Nannoplankton 
(or  Dwarf-plankton).  They  are  so  minute  that  they  pass 
easily  through  the  meshes  of  the  finest  silk  gauze,  and 
they  are  best  collected  by  centrifuging  samples  of  the 
water  at  a  high  rate  of  speed.  Their  importance  lies  in 
their  extremely  rapid  multiplication  and  in  the  fact  that 
some  of  them  are  producers  of  the  organic  out  of  the  inor- 
ganic, while  others  are  middlemen  between  the  dead  and 
the  living. 

The  securely  established  general  idea  of  fundamental 
importance  is  that  which  Liebig  did  much  to  promulgate 
— the  idea  of  the  circulation  of  matter.  Apart  from  a 
few  permanent  products  like  the  Travertine  of  Tivoli, 
the  oolitic  material  on  the  shores  of  the  Great  Salt  Lake, 
and  deposits  of  siliceous  diatom-earth,  everything  about 
the  lake  is  in  a  state  of  flux.  Place  a  box  with  water, 
some  mud,  and  some  animal  manure  beside  the  fish  pond, 
and  arrange  it  so  that  there  may  be  a  periodic  discharge 
from  near  the  surface.  Bacteria  multiply  and  work  their 
way  with  the  manure  ;  Infusorians  multiply  and  form  food 
for  Daphnids  and  other  '  water-fleas '  ;  these  trickle  in  a 
living  cascade  into  the  pond ;  the  fishes  are  fed,  and  the 
fisherman's  table  is  served.  The  chain  may  be  longer  or 
shorter  ;  Diatoms,  Rotifers,  Worms  and  so  on  may  share  in 
the  ceaseless  reincarnation  of  material  that  goes  on.  If  the 


FIG.  35. — Microscopic  organisms  of  the  dwarf  plankton  or '  Nannoplankton.'  (After 
Lohmann.)  1.  Halteria  rubra,  a  ciliated  Infusorian,  with  a  symbiotic  Alga 
inside  it.  2.  Meringosphaera  mediterranea,  a  unicellular  Alga,  with  long  pro- 
jecting processes.  3.  A  Chrysomonad  with  projecting  rods  on  its  shell.  4.  A 
Monad.  5.  Cladopyxis  setifera,  a  Peridinid  Infusorian.  6.  A  Coccolith, 
Rhabdosphsra  claviger.  7.  A  unicellular  Alga,  Chaetoceras  gracile.  8. 
Phytoflagellate,  Eutreptia. 


THE  HAUNTS   OF  LIFE  in 

fisherman  should  have  the  bad  luck  to  capsize  his  basket, 
he  might  get  the  contents  back  again  after  many  days. 
The  Bacteria  reduce  the  dead  fish  to  debris  which  Infu- 
sorians  devour,  and  to  simple  substances  which  plants 
reintroduce  into  the  circle  of  life.  What  was  part  of 
the  dead  fish  becomes  part  of  Infusorian  and  Diatom  ;  it 
enters  into  a  new  incarnation  in  the  Crustacean ;  it  be- 
comes again  part  and  parcel  of  a  fish.  For  it  is  thus 
that  the  world  goes  round,  and  we  have  a  curious  bio- 
logical commentary  on  casting  bread  upon  the  waters. 

An  extraordinary  outburst  of  vegetative  life  is  sometimes 
seen  in  canals,  extending  for  many  miles,  and  making 
the  water  like  green  soup.  The  phenomenon  is  due  to 
various  kinds  of  green  Algae,  but  often  it  is  one  kind  that 
predominates.  When  this  is  Oscillator ia,  the  sight  is 
especially  remarkable,  for  this  type  of  filamentous  blue- 
green  Alga  has  the  habit  of  slowly  bending  backwards  and 
forwards  in  the  water — as  if  it  were  trying  to  break  its 
vegetative  chains. 

Origin. — When  we  ask  in  regard  to  a  freshwater  basin, 
where  its  tenants  came  from,  we  are  led  to  three  answers. 
(1)  It  seems  quite  clear  that  a  certain  number  have  come 
from  the  sea,  either  by  active  migration,  as  we  see  the 
elvers  doing  to-day,  or  by  passive  transport  as  in  the  case 
of  the  freshwater  sponges.  When  we  find  one  family  of 
sponges  (Spongillidse)  in  freshwater,  and  a  large  number 
of  families  in  the  sea,  we  may  safely  conclude  that  the 
freshwater  forms  had  a  marine  ancestry.  Hydra  and  half 
a  dozen  other  Hydrozoa  live  in  freshwater  ;  all  the  other 
Co3lentera  or  stinging  animals  are  marine ;  we  need  have 
no  hesitation  in  regarding  the  freshwater  forms  as  derived 
from  marine  ancestors. 


H2  THE  WONDER  OF  LIFE 

It  seems  very  likely  that  not  a  few  of  the  freshwater 
animals  have  migrated  gradually  from  the  sea  and  the  sea- 
shore, through  estuaries  and  brackish  water,  to  rivers 
and  lakes.  As  the  possibility  of  making  this  transition 
depends  on  the  physiological  constitution  of  the  animal, 
we  can  understand  that  similar  forms  would  succeed  in 
different  areas.  And  this  is  part  of  the  explanation  of 
the  high  degree  of  uniformity  seen  in  the  freshwater  faunas 
of  widely  separated  areas.  The  process  of  migration  may 
be  seen  going  on  at  present  in  the  invasion  of  the  Kiel 
Canal  and  in  some  similar  cases.  Various  shrimps  and 
the  like  go  far  up  certain  rivers ;  the  flounder  is  found 
many  miles  from  the  sea  ;  sticklebacks  seem  to  be  quite 
capable  of  thriving  well  in  either  fresh  water  or  salt ;  and 
there  are  hundreds  of  similar  facts. 

(2)  It  has  been  suggested  by  Credner,  Sollas  and  others 
that  some  present-day  lakes  are  dwindling  remnants  of 
ancient  seas — relict- seas  in  short.  Part  of  an  old  sea 
may  become  land-locked  and  be  converted  in  course  of 
time  into  a  freshwater  basin.  Or  it  may  be  that  a  present- 
day  lake  which  never  was  as  such  part  of  a  sea,  may  be- 
come connected  with  a  relict-sea  by  alterations  of  land- 
level  and  owe  part  of  its  fauna  to  that  circumstance. 
There  may  have  been  a  somewhat  uniform  pelagic  fauna 
in  the  remote  past,  and  that  may  be  part  of  the  explanation 
of  the  uniformity  of  the  fauna  in  freshwater  basins  widely 
separated  from  one  another.  If  the  land-locked  portion 
of  sea  was  gradually  converted  into  a  freshwater  basin, 
there  would  be  a  stern  elimination  of  non-plastic  types, 
and  since  the  conditions  of  elimination  would  be  much 
the  same  everywhere,  the  result  would  be  uniformity  in 
the  survivors.  Mr.  J.  E.  S.  Moore  has  brought  forward 


THE  HAUNTS  OF  LIFE  113 

strong  evidence  to  show  that  the  fauna  of  Lake  Tanganyika 
includes  many  molluscs,  for  instance,  which  were  inhabi- 
tants of  Jurassic  seas.  It  is  very  striking  to  find  in  Lake 
Tanganyika  a  Gasteropod  like  Typhobia  horei — whose 
kinship  is  certainly  with  marine  types. 

Several  different  kinds  of  freshwater  Medusoids  (Limno- 
codium,  Limnocnida)  are  known  from  various  parts  of 
the  world,  and  are  probably  to  be  interpreted  as  relicts  of 
a  marine  stock.  The  same  may  be  said  of  the  very  simple 
freshwater  polyp,  Microhydra  ryderi,  reported  from  North 
America  and  also  from  Germany.  Like  numerous  marine 
hydroids,  but  unlike  the  common  freshwater  Hydra,  it 
liberates  a  minute  swimming-bell  or  Medusoid. 

It  is  necessary  to  distinguish  between  relict  marine 
faunas  and  relict  seas.  Thus  the  remarkable  population 
of  Lake  Baikal  seems  to  be  in  part  a  relict  marine  fauna, 
but  there  is  no  evidence  in  the  surrounding  deposits  to 
show  that  the  Lake  was  ever  anything  but  a  freshwater 
basin.  We  must  therefore  suppose  that  the  marine  types 
in  the  lake — the  seals,  for  instance — migrated  from  an 
ancient  sea,  along  paths  now  hidden. 

Thirty-four  fishes  are  known  from  Lake  Baikal,  and 
L.  S.  Berg  divides  them  into  those  which  are  general  in 
Siberian  freshwaters  (17)  and  those  (also  17)  which  are 
endemic.  Of  the  latter  some  are  related  to  Siberian  forms, 
while  others  (Abyssocotini,  Cottocomephoridse  and  Come- 
phoridse)  seem  quite  unique.  There  are  no  forms  in  the 
Siberian  waters,  nor  in  the  Arctic  Ocean,  nor  in  the  Pacific 
which  come  near  these  puzzling  forms  which  Berg  regards 
as  very  ancient,  and  perhaps  native  (autochthonous)  to 
the  Lake.  They  live  at  greater  depths  than  any  other 
freshwater  fishes,  descending  to  1,600  metres. 

i 


ii4  THE  WONDER  OF  LIFE 

(3)  Of  many  of  the  smaller  animals  in  a  freshwater  basin, 
it  is  safe  to  say  that  they  have  been  transported  from  some 
similar  haunt.  The  same  or  similar  species  occur  in  basins 
separated  by  half  the  circumference  of  the  globe.  And 
just  as  there  are  distinctive  species  of  mammals  and  birds 
in  islands — e.g.  the  Orkney  Vole  and  the  St.  Kilda  Wren 
— so  there  are  distinctive  species  of  crustaceans  and  fishes 
in  lakes,  the  explanation  being  in  both  cases  the  same,  that 
local  variations  have  been  helped  by  isolation  to  become 
stable  species.  A  very  striking  instance  may  be  found  in 
the  large  number  of  different  species  of  char  in  British  lochs. 

To  explain  the  widespread  faunistic  uniformity  in  fresh- 
water basins,  Darwin  referred  to  the  agency  of  birds  in 
carrying  organisms  or  germs  of  organisms  from  one  fresh- 
water basin  to  another,  from  one  watershed  to  another ; 
to  the  wafting  powers  of  the  wind  ;  and  to  changes  of  land 
level  which  may  bring  different  river  beds  into  communica- 
tion. The  capture  of  one  river- valley  by  another  running 
in  a  different  direction  has  often  occurred,  and  may  have 
helped  to  distribute  lacustrine  types.  It  is  probable, 
however,  that  birds  have  been  the  chief  agents  in  transport. 
The  startled  duck  that  rises  in  a  hurry  from  the  water 
often  carries  some  entangled  aquatic  plants  with  it,  and 
animals  on  the  plants.  Thus  another  pond  may  be  peopled. 
In  the  clodlets  of  mud  on  the  feet  of  birds  many  minute 
animals  have  been  found — Ostracods,  Phyllopods  and 
Copepods  (all  sorts  of '  water-fleas  '  in  short),  Polyzoa  and 
Rotifers,  and  Nematode  worms.  No  fewer  than  537 
plants  were  found  represented  in  6|  ounces  of  mud,  and 
Darwin  got  eighty  seeds  to  germinate  from  one  clodlet 
from  one  bird's  foot.  The  role  of  birds  as  distributing 
agents  is  well  known  to  be  very  important  for  seeds,  but 


THE  HAUNTS  OF  LIFE  115 

it  is  also  very  important  for  small  animals.  A  diagrammatic 
instance  may  be  found  in  the  occurrence  of  a  freshwater 
sponge  in  a  pond  in  the  middle  of  the  sandy  Sable  Island 
which  lies  out  in  the  Atlantic,  a  hundred  miles  from  Nova 
Scotia. 

From  Land  or  Air  back  to  Water. — There  is  a 
certain  contingent  of  the  freshwater  fauna  that  has  arisen 
by  a  sort  of  turning  back  of  terrestrial  and  aerial  forms. 
Just  as  whales  and  dolphins  are  in  all  probability  the 
descendants  of  terrestrial  mammals  which  took  secondarily 
to  the  sea,  so  some  freshwater  animals,  such  as  aquatic 
insects,  the  water-shrew  and  the  water-vole,  the  otter  and 
the  beaver,  are  doubtless  the  descendants  of  terrestrial  forms. 

In  this  connexion  it  may  be  noted  that  many  water 
animals  are  not  so  much  wetted  as  one  might  think.  In 
some  water-beetles,  such  as  the  whirligig  (Gyrinus]  and  the 
water  boatman  (Notonecta),  the  body  is  very  partially 
wetted.  In  the  water-spider  (Argyroneta)  considerable 
areas  of  the  hairy  body  refuse  to  become  wet.  In  the  family 
of  Hydrophilid  beetles,  some  hardly  wet  at  all,  some  keep 
considerable  parts  of  the  body  dry,  and  some  become  wholly 
wet.  The  wetting  or  not  wetting  depends  on  capillary 
phenomena,  which  depend  on  the  structure  of  the  surface 
of  the  body  and  its  hairs  or  setae.  There  can  be  little 
doubt  that  the  differences  are  finely  adaptive  to  slight 
differences  in  habit. 

The  Water- Spider. — In  illustration  of  the  interesting 
habits  of  freshwater  animals  we  may  take  the  case  of 
the  water-spider,  Argyroneta  natans,  of  which  Dr.  Wagner 
has  made  a  fine  study.  It  is  remarkable  as  an  air-breather 
which  spends  most  of  its  life  under  water,  and  it  is  remark- 
able among  spiders  inasmuch  as  the  male  is  much  larger 


n6  THE  WONDER  OF  LIFE 

than  the  female.  The  length  of  the  male's  body  is  about 
15  mm.  and  that  of  the  female  about  8  mm.  The  colour 
is  reddish-brown  to  olive-brown,  but  it  has  when  swimming 
a  silvery  appearance  due  to  bubbles  of  air  which  are 
entangled  among  the  velvety  hairs  and  shreds  of  silk  which 
cover  the  body.  It  is  in  quiet  pools  where  there  are  abun- 
dant water- weeds  that  this  member  of  a  thoroughly  terres- 
trial race  makes  itself  at  home.  There  are  a  few  other 
spiders,  e.g.  species  of  Dolomedes  and  Pirata,  which  creep 
down  plants  right  into  the  water  when  danger  threatens,  and 
there  are  a  few  others  which  walk  daintily  on  the  surface- 
film,  but  Argyroneta  is  the  only  thoroughly  sub-aquatic  type. 
It  makes,  as  every  one  knows,  a  dome-shaped  web,  usually 
attached  by  silk  threads,  like  a  tent  by  its  ropes,  to  water- 
weeds  and  stones,  but  occasionally  fashioned  inside  a  water- 
snail's  empty  shell,  or  in  a  hole  in  a  piece  of  wood.  In  all 
cases  it  fills  its  dome  with  air  brought  down  from  the  sur- 
face, till  the  result  is  something  between  a  diving-bell  and 
a  submerged  balloon.  It  has  anticipated  at  least  one  of 
man's  many  inventions,  though  it  is  probably  but  dimly 
aware  of  its  inherited  or  instinctive  skilfulness.  There 
is  no  hint  of  prentice- work  in  the  web  that  is  made  in  such 
peculiar  conditions,  and  it  is  interesting  to  notice  that  the 
architecture  bears  a  close  resemblance  to  that  of  the  webs 
made  by  terrestrial  members  of  the  same  family.  For  some 
reason  or  other,  the  pattern  worked  out  in  winter  is  different 
from  that  of  the  summer  web.  The  webs  require  frequent 
renewal,  for  inquisitive  Gammarids  and  the  like  are  con- 
tinually breaking  the  moorings.  The  supply  of  air  has 
also  to  be  continually  renewed.  With  this  work  and  with 
the  pursuit  of  the  water-insects  on  which  it  feeds,  the 
spider  is  kept  busy,  but  it  is  able  to  spare  a  good  deal  of 


THE   HAUNTS  OF  LIFE  117 

time  for  its  toilet — not  exactly  in  combing  its  hair,  as  its 
movements  suggest,  but  in  arranging  its  lace,  for  it  carries 
little  tags  of  silk  disposed  over  its  body. 

Unlike  most  spiders,  Argyroneta  is  very  peaceful,  as  if 
its  residence  in  water  had  cooled  its  passions.  When  two 
meet  they  go  quietly  on,  unless  they  are  worried  by  cap- 
tivity or  happen  to  be  very  hungry — when,  like  creatures 
of  higher  degree,  they  are  apt  to  be  quarrelsome.  The 
females  are  patterns  of  placidity,  and  are  quite  free  from 
the  reproach  of  devouring  their  mates  or  would-be  mates, 
as  their  terrestrial  cousins  often  do.  It  has  to  be  remem- 
bered in  this  connexion  that  they  are  only  about  half  the 
size  of  the  males,  the  reverse  of  the  usual  relative  propor- 
tions of  the  sexes  among  spiders.  Within  the  silken  bell 
the  mother  spider  carefully  disposes  the  cocoon  containing 
the  eggs,  but  when  these  hatch  and  the  young  spiders  begin 
to  fend  for  themselves,  she  ceases  to  show  any  interest 
in  their  movements.  Wagner  insists  that  she  cares  more 
about  the  cocoon  than  its  contents,  but  it  is  very  difficult 
to  get  mentally  near  these  children  of  instinct,  and  it  may 
be  that  the  impression  is  as  erroneous  as  that  which  might 
be  made  by  a  casual  observer  of  mankind  who,  looking 
down  from  a  great  height,  maintained  that  mothers 
seemed  to  give  more  attention  to  the  cradle  or  the  peram- 
bulator than  to  the  content  of  baby. 

V.    THE  TERRESTRIAL  FAUNA 

The  transition  from  water  to  dry  land  has  been  many 
times  effected  in  the  course  of  animal  evolution.  Among 
backboneless  animals,  it  was  negotiated  by  some  of  the 
Protozoa  (Amoebae  and  Infusorians)  that  passed  from  water 
to  damp  earth  ;  by  some  of  the  simpler  worm- types  (various 


n8  THE  WONDER  OF  LIFE 

Planarians  and  Nematodes) ;  by  the  earthworms  and  land- 
leeches  ;  by  a  few  Crustaceans,  such  as  wood-lice  and  land- 
crabs  ;  by  the  archaic  Peripatus  and  its  allies — widespread 
connecting-links  between  segmented  worms  and  types 
like  Centipedes  ;  by  the  Centipedes  themselves  and  their 
allies,  such  as  Millipedes  ;  by  many  Insects  ;  by  Spiders, 
Scorpions  and  many  Mites  ;  and  by  the  Pulmonate  Gastro- 
pods, namely  land-snails  and  land-slugs. 

While  fishes  are,  of  course,  confined  to  the  water,  there 
are  some  interesting  curiosities.  Thus  the  eel  may  make 
short  excursions  over  the  moist  grass  of  the  meadow, 
and  some  tropical  fishes  burrow  deep  into  the  mud  in 
the  dry  season.  In  the  common  Periophthalmus  of 
tropical  shores  we  have  one  of  those  extraordinary  excep- 
tional cases — a  fish  that  can  remain  for  many  hours  out 
of  water.  The  same  is  true  of  the  interesting  double- 
breathing  mud-fishes  (Dipnoi),  which  have  their  swim- 
bladder  turned  into  a  sort  of  lung,  and  can  live  long  out 
of  water.  Among  backboned  animals,  the  transition  from 
aquatic  to  terrestrial  life  was  made  in  the  Carboniferous 
Period  by  the  Amphibians,  many  of  which  still  recapitulate 
every  year  the  historically  important  step — passing  from 
a  larval  or  tadpole  gill-breathing  life  in  the  water  to  an 
adult  lung-breathing  life  on  land.  In  a  few  cases,  e.g. 
the  black  salamander  (Salamandra  atra)  of  the  Alps,  which 
lives  above  the  level  of  water-pools,  and  some  tree-frogs 
which  never  come  to  earth,  the  aquatic  gill-breathing  stage 
is  skipped  altogether. 

In  Reptiles,  Birds,  and  Mammals,  as  every  one  knows, 
there  is  no  trace  of  gills  left  in  early  life  (though  the  tell- 
tale gill-clefts  remain  in  the  embryo),  and  the  young  are 
lung-breathers  from  the  time  they  are  born  or  hatched.  A 


THE  HAUNTS  OF  LIFE  119 

secondary  return  to  the  water  is  illustrated  by  some  Reptiles 
— water-snakes,  turtles,  crocodilians  and  a  single  marine 
lizard  (Amblyrhynchus) ;  by  some  birds  like  the  flightless 
penguins  and  the  pelagic  petrels ;  by  some  mammals  like 
Cetaceans  and  Sirenians,  seals  and  sea-lions. 

Origin. — Some  terrestrial  animals  probably  passed 
from  the  freshwaters,  through  the  mediation  of  marsh 
and  bog.  The  earthworms  form  a  large  cosmopolitan 
group,  now  thoroughly  terrestrial  and  indeed  avoiding 
very  wet  places,  but  the  occurrence  of  three  or  four  aberrant 
types  (like  Alma  and  Dero)  with  gills  tells  the  tale  of  their 
historical  origin.  No  one  can  doubt  that  the  land-leeches 
were  derived  from  a  freshwater  stock,  for  the  great  majority 
of  leeches  (Hirudinea)  are  tenants  of  the  freshwaters.  It 
is  probable  that  the  snails  and  slugs  of  dry  land  originated 
from  a  freshwater  stock  and  there  is,  of  course,  no  dubiety 
in  cases  like  frogs  and  toads  where  the  larval  life  is  still 
spent  in  the  ponds  and  ditches.  The  interesting  land-crab, 
Birgus  latro,  which  goes  far  up  the  mountains  and  even 
climbs  trees,  returns  every  year  to  the  sea-shore  to  breed, 
and  its  marine  larvae  well  illustrate  the  general  conclusion 
that  the  habitat  of  the  young  forms  is  the  ancestral  habitat. 
It  is  possible  that  the  terrestrial  Isopods  were  also  derived 
from  a  littoral  stock. 

If  a  land-animal  has  not  originated  from  a  freshwater 
stock  or  from  a  littoral  stock,  how  else  could  it  arise  ? 
The  third  mode  of  origin  is  from  some  pre-existing  terres- 
trial stock.  Thus  Mammals  probably  evolved  from  a 
terrestrial  Reptile  stock,  and  Reptiles  from  a  terrestrial 
Amphibian  stock.  Thus,  again,  it  is  probable  that  Insects 
and  Spiders  sprang  from  pre-existing  terrestrial  stocks  of 
Arthropods. 


I2o  THE  WONDER  OF  LIFE 

Fundamental  Adaptations. — Prof.  Cuenot  has  noted 
that  there  are  four  adaptations  essential  to  thoroughly 
terrestrial  life.  (1)  The  animal  must  be  able  to  breathe 
dry  air,  either  by  the  skin  (as  in  earthworms),  or  by  some 
special  apparatus,  such  as  the  air-tubes  of  insects,  the 
lung-books  of  scorpions,  the  pulmonary  chamber  of  snails, 
and  the  true  lungs  of  Amphibians,  Reptiles,  Birds  and 
Mammals.  (2)  The  animal  must  be  able  to  resist  a  con- 
siderable range  of  variation  in  temperature  and  humidity, 
and  thus  we  find  in  terrestrial  animals  all  sorts  of  cuticular 
and  integumentary  structures,  such  as  feathers  and  hairs, 
and  all  sorts  of  detailed  devices  for  meeting  the  notable 
changes  in  vital  conditions  that  the  succession  of  the 
seasons  involves.  Thus  hibernation  and  warm-blooded- 
ness  find  their  place  here  as  exceedingly  effective  adapta- 
tions to  terrestrial  life.  (3)  A  terrestrial  animal  will  tend 
to  have  an  abbreviated  life-history,  or  in  other  words  a 
direct  development,  for  the  conditions  of  life  on  land  are 
not  suited  for  larval  stages.  The  notable  exception  is  in 
the  case  of  insects,  many  of  which  must  be  called  terres- 
trial, and  many  of  which  have  intricate  life-histories  with 
a  great  variety  of  larvse.  It  will  be  noted,  however, 
that  many  insect  larvse  are  very  carefully  hidden  away, 
that  many  are  specially  adapted  to  be  inconspicuous,  and 
that  many  are  peculiarly  protected  from  possible  enemies, 
e.g.  by  being  unpalatable,  by  being  covered  with  irrita- 
ting hairs,  by  exuding  repulsive  fluids.  On  the  whole, 
it  is  safe  to  say  that  it  is  characteristic  of  terrestrial 
animals  that  the  young  are  born  or  hatched  at  a  very 
advanced  state.  What  comes  out  of  the  egg  of  a  spider 
or  a  snail  is  a  miniature  of  the  adult,  fully  formed.  Some 
species  of  Peripatus  and  many  insects  are  viviparous.  In 


THE  HAUNTS  OF  LIFE  121 

many  birds  that  nest  on  the  ground,  the  young,  known 
as  Praecoces,  are  able  to  run  about  within  a  short  period 
after  hatching ;  and  every  one  knows  how  quickly  a 
lamb  or  a  foal  gets  on  to  its  legs. 

In  this  connexion  it  is  very  interesting  to  notice  that  in 
Amphibians  which  represent  the  transition-class  between 
aquatic  and  terrestrial  life,  there  are  not  a  few  exceptions 
in  which  the  larval  period,  normally  passed  through  in  the 
water,  tends  to  be  abbreviated  by  some  peculiar  device. 
Thus  the  eggs  of  the  South  American  Nototrema  ovifera 
are  pushed  by  the  male,  after  they  are  laid,  into  a  pocket 
on  the  female's  back ;  those  of  the  Chilian  Rhinoderma 
are  carried  by  the  male  in  his  resonating  sacs ;  those 
of  the  Surinam  Toad  develop  in  a  multitude  of  little  skin- 
pits  on  the  female's  back. 

(4)  The  fourth  adaptation  is  one  that  might  not  naturally 
occur  to  the  non-zoological  student.  A  thorough-going 
terrestrial  animal  usually  shows  internal  fertilization  of  the 
eggs.  In  many  fishes  the  eggs  are  deposited  in  the  water 
and  the  fertilizing  fluid  or  milt  is  deposited  upon  them  or 
near  them.  But  this  is  incompatible  with  the  conditions 
of  terrestrial  life.  There  are  exceptional  cases,  it  Is  true, 
but  they  tend  to  prove  the  rule.  Thus  one  earthworm 
fertilizes  another,  but  the  sperms  are  extruded  again 
in  packets  which  project  as  tiny  tags  on  the  skin  ;  these 
spermatophores  are  included  in  a  barrel  of  mucus  that 
slips  over  the  earthworm's  head  and  forms  the  cocoon  when 
the  eggs  are  liberated.  What  is  laid  in  the  ground  is  a 
cocoon  containing  several  eggs  and  numerous  sperms. 

The  terrestrial  area  has  to  be  divided  up  into  more  sub- 
divisions than  any  other  haunt  of  life  :  it  is  so  extraordinarily 
diverse.  We  think,  for  instance,  of  mountains  and  islands, 


122  THE  WONDER  OF  LIFE 

of  woods  and  forests,  of  moors  and  meadows,  of  links  and 
dunes — each  with  its  characteristic  fauna  and  flora.  There 
are  peculiar  regions  like  steppes  and  prairies,  tundra  and 
desert,  and  the  circum-  polar  areas  so  far  as  these  can  be 
called  terrestrial. 

Under  Ground. — It  is  interesting  to  think  of  the  large 
number  of  animals  that  have  taken  to  a  subterranean 
mode  of  life  as  burrowers  in  the  ground.  There  must  have 
been  long  ago  a  golden  age  for  the  race  of  earthworms 
when  they  discovered  the  possibility  of  colonizing  a  new 
world  below  the  surface.  Ages  probably  passed  before 
they  were  followed  by  the  Centipedes  who  are  their  invet- 
erate enemies,  by  some  of  the  burrowing  beetles,  and  by 
carnivorous  slugs  (Testacella).  Long  ages  passed  before 
the  moles  followed  the  earthworms  into  the  recesses  of 
the  soil,  and  became  equally  well  adapted  to  the  peculiar 
conditions  of  that  strange  mode  of  life. 

Over  and  over  again  the  same  story  has  been  re-enacted, 
e.g.  by  burrowing  amphibians  (Csecilians),  burrowing 
lizards  (Amphisbsenids),  and  burrowing  snakes  (Typhlops, 
etc.) :  a  temporary  safety  has  been  secured  by  a  change 
of  habitat,  and  then  new  enemies  and  difficulties  have  been 
encountered. 

Cave  Animals. — Caves  and  grottos  have  come  to  be 
tenanted  by  a  diverse  array  of  animals,  more  or  less  adapted 
to  the  conditions  of  life — darkness  and  constant  temperature, 
absence  of  green  plants,  and  a  humid  atmosphere,  for 
thoroughly  dry  caves  have  never  more  than  casual  tenants. 
The  cave-fauna  includes  many  bats,  a  few  peculiar  mice, 
the  Amphibian  Proteus  of  the  great  caves  of  Carniola  and 
Dalmatia,  and  three  American  salamanders,  a  good  many 
small  fishes,  numerous  beetles  and  a  few  other  kinds  of 


THE  HAUNTS  OF  LIFE  123 

insects,  many  spiders  and  crustaceans,  various  snails,  and 
so  on.  They  tend  to  be  somewhat  dwarfed  types,  with 
more  or  less  degenerate  eyes  (except  in  the  bats  and  mice), 
with  highly  developed  tactility,  and  with  reduced  pigmenta- 
tion. In  those  cavernicolous  animals  in  which  the  develop- 
ment of  the  eye  has  been  worked  out,  e.g.  Proteus,  Ambly- 
opsis  (a  fish),  and  Cambarus  (a  crayfish),  it  has  been  shown 
that  the  eye  of  the  young  form  is  relatively  less  degenerate 
than  that  of  the  adult. 

Racovitza,  who  has  made  a  special  study  of  cave-animals, 
gives  an  interesting  account  of  an  Isopod  or  wood-louse, 
Spela3oniscus,  from  an  Algerian  cavern.  It  is  colourless, 
blind,  and  covered  with  tactile  setse  ;  it  has  no  longer  any 
near  relatives  living  in  the  light  of  day ;  it  is  an  archaic 
representative  of  a  fauna  which  has  disappeared.  It  was 
in  a  sense  a  failure,  Kacovitza  thinks,  for  whereas  it  can 
roll  itself  up  in  a  ball  like  many  other  Isopods,  such  as 
the  widely  distributed  Armadillidium  vulgare,  its  antennae 
are  left  sticking  out  and  exposed  to  danger.  So  it  had 
to  become  a  Troglodyte.  Eacovitza  suggests  that  it  is 
not  the  only  failure  who  has  taken  refuge  in  a  cave,  '  cet 
asile  que  dame  nature  installa  a  peu  de  frais  pour  ses  veil- 
lards,  ses  impotents  et  ses  rates'. 

VI.    THE  AERIAL  FAUNA 

The  last  haunt  of  life  to  be  tenanted  was  the  air,  and 
it  is  interesting  to  notice  how  many  attempts  have  been 
made  to  possess  it.  Among  backboneless  animals  the 
insects  alone  have  attained  to  the  power  of  true  flight,  but 
among  backboned  animals  there  are  three  instances  of 
success — the  extinct  Pterodactyls,  the  Flying  Birds,  and 
the  Bats.  Thus  in  each  of  the  three  great  classes  of  air- 


124  THE  WONDER  OF  LIFE 

breathing  Vertebrates— Reptiles,  Birds  and  Mammals — 
the  problem  of  flight  has  been  solved,  each  time  in  a 
different  way. 

The  power  of  taking  '  soaring  '  leaps  has  been  acquired 
many  times  over  in  the  history  of  Vertebrates.  R.  S. 
Lull  gives  ten  cases — Rhacophorus,  Ptychozoon  (a  lizard 
with  a  long  fringed  tail),  Draco  (a  lizard  with  the  skin 
extended  on  greatly  prolonged  ribs),  and  seven  Mammals, 
Petauroides,  Petaurus,  Aerobates,  Anomalurus,  Pteromys, 
Galeopithecus  and  Propithecus.  Except  in  Petauroides, 
there  is  in  these  swooping  mammals  a  fold  of  skin  along 
the  animal's  flanks,  which  may  be  supplemented  by 
folds  in  front  of  the  fore-limbs,  between  the  hind  limbs, 
or  along  the  tail.  In  the  much-debated  movements 
of  the  Flying  Fishes  (Thoracopterus,  Gigantopterus, 
Exocoetus,  and  Dactylopterus),  there  is  at  most  an 
approximation  to  true  flight. 

It  is  not  surprising  that  many  of  the  attempts  to  possess 
the  air  should  have  proved  quite  unsuccessful,  for  man's 
own  experience  of  aviation  has  taught  him  that  success 
depends  on  numerous  fine  adjustments,  and  is  not  to  be 
attained  except  at  great  cost  of  life.  In  the  case  of  birds 
there  is  a  remarkable  correlation  of  numerous  adaptations 
— the  somewhat  boat-like  shape  of  the  body,  the  ballasting 
of  the  body  with  heavy  organs  below,  the  lightly  built 
skeleton  with  bones  of  the  hollow  girder  type,  the  arrange- 
ment by  which  the  flying  helps  the  breathing,  the  enormous 
development  of  the  pectoral  muscles  sometimes  attaining  to 
half  the  whole  weight  of  the  bird,  the  turning  of  an  arm  into 
a  wing,  the  possession  of  feathers  with  inter-linked  barbs, 
the  fusion  of  dorsal  vertebrao  to  form  a  steady  basis  against 
which  the  wings  can  work,  and  so  on  through  a  long  list. 


THE  HAUNTS   OF  LIFE  125 

From  the  evolutionist  point  of  view  it  is  interesting 
to  notice  that  in  Bird,  Bat  and  Pterodactyl  the  flying 
organ  is  in  each  case  the  arm,  and  yet  the  details  of  the 
transformation  are  very  different  in  the  three  cases.  With 
precisely  the  same  fundamental  material  to  work  with, 
three  entirely  different  types  of  wing  have  been  evolved. 

In  insects  the  wings  appear  to  be  entirely  novel  struc- 
tures— hollow,  flattened  sacs  growing  out  from  the  upper 
parts  of  the  two  posterior  divisions  of  the  thorax ;  but  it 
is  possible  that  they  were,  to  begin  with,  rather  respiratory 
than  locomotor  organs.  Indeed,  in  some  cases  they  still 
have  considerable  respiratory  function — containing  blood- 
channels  and  extensions  of  the  air-tubes  or  tracheae.  As 
illustrations  of  analogy  it  is  interesting  to  compare  Birds 
and  Insects,  for  they  are  as  far  apart  from  one  another 
anatomically  as  they  could  well  be,  and  yet  they  have 
much  in  common — lightly  built  bodies,  highly  specialized 
musculature,  very  elaborate  respiratory  system  with  active 
expiratory  movements,  and  so  on.  These  are  convergent 
adaptations  towards  the  same  end  in  entirely  different 
types. 

It  is  probable  that  the  Vertebrate  animals  which  have 
attained  to  the  power  of  true  flight  have  sprung  from 
arboreal  stocks.  It  is  likely  that  the  oldest  known  bird 
— the  extinct  Archaeopteryx — which  had  teeth  on  both 
jaws,  a  long  lizard- like  tail,  and  claws  on  each  of  the  three 
digits  of  the  half-made  wing,  was  definitely  arboreal.  The 
same  conclusion  is  suggested  by  the  Hoatzin  (Opistho 
comus),  one  of  the  most  primitive  of  living  birds,  whose 
young  ones  clamber  about  on  the  branches.  It  is  probable 
that  the  Bats  sprang  from  a  stock  of  arboreal  Insectivores. 

Most  of  the  insects  which  are  aerial  as  adults  spend  the 


126  THE  WONDER  OF  LIFE 

early  part  of  their  life  on  the  ground,  or  on  herbs  and 
bushes,  or  in  the  water,  for  the  possession  of  the  air  is, 
of  course,  a  secondary  victory.  It  is  interesting  to  notice, 
however,  how  very  independent  of  the  earth  many  of 
the  birds  have  become,  with  even  their  nests  far  off  the 
ground.  How  thoroughly  aerial  a  bird  may  be  is  well 
illustrated  by  the  common  swift,  which  throughout  the 
long  summer  daylight  never  alights  or  pauses,  except  for 
brief  moments  at  the  nest. 

Gossamer. — In  illustration  of  successful  adventure  into 
the  air,  the  flights  of  gossamer- spiders  may  be  noticed.  At 
various  times  throughout  the  year,  but  especially  in  the 
autumn,  large  numbers  of  small  spiders  congregate  on  the 
tops  of  palings  and  bridge-rails  and  herbage,  and  standing 
on  tiptoe  with  their  head  to  the  breeze,  allow  long  threads 
of  silk  to  pass  from  their  spinnerets.  When  the  parachute 
is  long  enough  and  the  wind  begins  to  pull  on  it,  the  spiders 
let  go  their  hold  of  their  support,  and  are  borne  on  the 
wings  of  the  wind  from  one  parish  to  another.  If  the 
wind  should  fall,  the  spiders  can  *  spread  more  sail '  by 
lengthening  their  silken  threads.  If  the  wind  should  rise, 
the  spider  can  '  furl  their  sails  '  by  winding  in  part  of  their 
parachute.  When  tens  of  thousands  of  small  spiders 
migrate  simultaneously  some  fine  morning,  there  may 
be,  as  they  sink  to  earth,  a  shower  of  gossamer,  covering 
the  fields  for  acres.  In  many  cases  we  see  and  feel  threads 
of  gossamer  floating  in  the  air  without  any  attached  spiders  ; 
these  are  usually  broken-off  parts  of  parachutes.  They 
recall  to  us  the  failures  of  the  days  before  achievement. 


CHAPTER  III 

THE  INSURGENCE  OF  LIFE 

(THE  CIRCUMVENTION  OF  SPACE  AND  THE  CONQUEST 
or  TIME) 

'  Sbe  is  tbe  onlg  artist ;  worfcing=up  tbe  most  uniform 
material  into  utter  opposites ;  arriving,  without  a  trace  of 
effort,  at  perfection,  at  tbe  most  ejact  precision,  tbougb 
always  veileo  unDer  a  certain  softness.  .  .  .' 

'Sbe  is  all  tbings.  .  .  .  sbe  is  rougb  ano  tenoer,  lovely 
ano  bateful,  powerless  ano  omnipotent.  .  .  / 

'Sbe  is  cunning,  but  for  gooo  enos;  ano  it  is  best  not  to 
notice  ber  trtcfcs.  .  .  / 

4  &be  one  tbing  sbe  seems  to  aim  at  is  5noi\>tDualitg ;  vet 
sbe  cares  notbing  for  inDfviouals.  Sbe  is  always  builofng 
up  ano  Destroying;  but  ber  worfcsbop  is  inaccessible.' 

— Goethe's  Aphorisms,  translated  by  Huxley. 

Productivity — Filling  every  niche — Difficult  Conditions — Tenacity 
of  Life — Plasticity — The  Biology  of  the  Seasons — Migration 
as  an  Instance  of  Insurgence. 

IN  many  of  its  familiar  expressions  life  seems  to  be  an 
extraordinarily    delicate    form    of     activity — easily 
disturbed  and  spoilt  and  ended.     A  little  quickening  of  the 
rate  of  metabolism,  and  life's  fitful  fever  is  over.     A  slight 
lack  of  harmony  in  the  internal  laboratory,  and  the  happy 
child  becomes  a  cretin.      A  pin-prick  below  the  thumb- 
nail when    he   was  planting    seedlings    and    the    robust 
gardener  dies  of  lockjaw.     An  unusually  cold  night  and  two 
127 


128  THE  WONDER  OF  LIFE 

hundred  birds  are  gathered  in  the  morning  in  one  stackyard. 
This  does  not  sound  much  like  the  insurgence  of  life  ! 

It  must  be  pointed  out,  however,  that  the  impression 
we  often  get  of  the  brittleness  of  living  creatures  is  apt  to  be 
fallacious.  Truly  the  more  intricate  of  them  have  ex- 
quisitely balanced  organizations,  with  machinery  that  is 
easily  put  out  of  gear,  for  the  more  parts  there  are,  the 
greater  is  the  likelihood  of  something  going  wrong,  and 
chemical  complexity  often  involves  chemical  instability. 
But  the  big  fact  is  that  life  is  tough. 

A  boy  whirling  a  stick,  a  pigeon  strutting  on  the  ground,  a 
fortuitous  contact  between  boy's  stick  and  pigeon's  skull, 
and  it  is  all  over  with  the  favourite  bird.  This  is  a  trivial 
instance  of  what  in  the  course  of  life  we  have  far  too 
many  occasions  to  deplore,  namely  casualties.  Socially,  a 
casualty  means  an  accident  for  which  no  one  in  particular 
is  to  blame  ;  it  is  put  down  to  '  the  hand  of  God '.  Bio- 
logically expressed,  a  casualty  is  a  fortuitous  and  fatal 
incidence,  on  a  living  creature,  of  forces  to  which  it  cannot 
in  any  effective  way  respond.  It  is  plain  enough  that  if 
the  pigeon  had  only  had  the  skull  of  an  elephant,  or  a  ram 
for  that  matter,  it  would  not  have  died  from  a  slight  '  con- 
cussion of  the  brain  '  induced  by  the  schoolboy's  carelessly- 
handled  stick.  But  then  it  would  not  have  been  a 
pigeon,  and  could  not  have  been  a  pigeon,  for  the  real 
answer  to  the  apparent  difficulty  is  that  complex  organisms 
cannot  be  adapted  to  casual  dangers,  that  they  would  be 
unthinkably  handicapped  if  they  were.  Therefore,  when 
we  think  of  the  terrible  destruction  in  the  fauna  of  the 
Gulf  of  Naples  after  an  eruption  of  Vesuvius,  or  the  decima- 
tion both  on  the  shore  and  inland  that  follows  an  unusually 
hard  winter,  we  are  forced  to  admit  that  we  cannot  expect 


THE   INSURGENCE  OF  LIFE  129 

organisms  to  be  adapted  to  resist  other  than  normal  con- 
ditions. Our  expectations  are  often,  however,  agreeably 
disappointed. 

We  admit,  then,  that  organisms  are  often  tender  plants, 
frail  edifices,  delicate  pieces  of  vital  machinery,  adapted 
for  a  relatively  constant,  or  at  any  rate  regular  environ- 
ment, and  not  for  casualties.  But  the  much  bigger  fact 
is  the  toughness  of  life,  which  we  wish  to  illustrate  in  this 
chapter.  It  is  difficult  to  get  a  fitting  word  for  the  quality 
that  impresses  us  all— the  self-assertiveness  of  life,  its  power 
of  persistence  against  difficulties,  its  habit  of  attempting 
the  apparently  impossible  and  leading  forlorn  hopes.  We 
have  called  it  the  insurgence  of  life. 

Perhaps  the  primary  illustration  of  the  quality  is  to  be 
found  in  the  fundamental  fact  about  life,  that  although  the 
organism  is  always  changing,  it  yet  remains  approximately 
the  same.  It  is  always  burning  away,  but  it  is  not  con- 
sumed. It  is  continually  arising  like  a  Phoenix  from  its 
own  combustion.  Ceaseless  metabolism  in  all  ordinary 
cases,  and  yet  a  retention  of  integrity  or  intactness — that 
is  the  fundamental  wonder  of  life.  To  this  we  shall  have 
to  return  in  our  final  chapter. 

PRODUCTIVITY 

In  illustration  of  what  we  venture  to  call  the  insurgence 
of  life,  we  may  begin  by  recalling  a  few  instances  of  pro- 
ductivity. Life  is  like  a  stream  that  is  continually  tending 
to  overflow  its  banks.  A  little  one  is  always  becoming  a 
thousand,  and  a  small  one  a  great  nation.  Some  of  us 
on  an  ocean  voyage  may  have  watched  the  sun  set  in  the 
water,  lingering  for  a  minute  or  two  like  a  ball  of  fire 
balanced  on  the  tight  string  of  the  horizon,  and  may  have 

K 


130  THE  WONDER  OF  LIFE 

waited  till  it  became  quite  dark  except  for  the  stars  and  the 
steamer  lights,  and  then  enjoyed  the  splendour  of  oceanic 
'  phosphorescence '.  There  is  a  cascade  of  sparks  at  the 
prow,  a  stream  of  sparks  all  along  the  water  level,  a  welter 
of  sparks  in  the  wake,  and  even  where  the  waves  break 
there  is  fire.  So  it  goes  on  for  miles  and  hours — a  lumin- 
escence due  to  the  rapid  vital  combustion  of  pinhead-like 
creatures  (Noctiluca  and  others),  so  numerous  that  a 
bucketful  contains  more  of  them  than  there  are  people  in 
London.  We  are  filled  with  amazement  at  the  prodigal 
abundance  of  life. 

Taking  the  slowest  breeder  among  mammals,  Darwin 
calculated  that  a  pair  of  elephants,  living  for  over  a  century 
and  rearing  one  offspring  every  ten  years,  would  have  in 
750  years,  barring  accidents,  nineteen  millions  of  descen- 
dants. Wallace  quotes  Kerner's  statement  that  a  common 
weed,  Sisymbrium  sophia,  often  has  three-quarters  of  a 
million  of  seeds,  and  that  if  these  all  grew  to  maturity  and 
seeded,  the  whole  of  the  land-surface  of  the  globe  would  be 
covered  with  the  result  within  three  years. 

The  very  general  absence  of  parental  care  of  any  sort 
among  fishes  is  a  familiar  fact,  partly  explicable  because 
fishes  are  creatures  of  low  degree  in  the  Vertebrate  alliance, 
and  partly  because  of  the  prolific  reproduction.  With  egg- 
laying  in  the  open  water  in  the  great  majority  of  cases, 
parental  care  would  be  difficult,  and  survival  is  secured  by 
great  reproductivity.  It  is  sometimes  extraordinary.  A 
ling  weighing  54  pounds  had  28,000,000  eggs,  a  turbot  of 
17  pounds  9,000,000  eggs,  a  cod  of  21£  pounds  6,000,000 
eggs.  In  four  herrings  the  number  of  eggs  varied  from 
20,000  to  47,000. 

In  many  of  the  less  differentiated  animals  there  is  not 


THE   INSURGENCE  OF  LIFE  131 

only  great  fertility,  but  rapid  coming  to  maturity.  Mr. 
Newton  Miller  has  supplied  precise  data  as  to  the  fertility 
of  the  brown  rat  in  captivity,  and  these  are  of  serious  human 
interest  because  of  the  importance  of  this  animal  as  a 
destroyer  of  food-supplies  and  a  disseminator  of  disease. 
The  creature  breeds  all  the  year  round,  and  five  or  six 
litters  may  be  actually  reared  by  a  pair  in  the  course  of  a 
year.  If  the  young  are  destroyed  or  removed  at  birth, 
there  may  probably  be  a  litter  every  month.  In  one  case 
seven  litters  were  produced  in  seven  months  by  one  female. 
The  young  are  carried  from  23|-25£  days  before  birth. 
The  number  in  a  litter  varies  from  six  to  nineteen,  with  an 
average  between  ten  and  eleven.  They  are  not  full  grown 
before  eighteen  months,  but  both  sexes  are  ready  for 
reproduction  not  later  than  the  end  of  the  fourth  month. 

The  rabbit  may  have  six  young  ones  in  a  litter,  and  four 
litters  in  a  year  ;  and  the  young  may  begin  to  breed  when 
they  are  six  months  old.  This  rate  is  far  surpassed  by 
some  of  the  mice,  and  when  we  descend  to  the  level  of 
insects  and  the  like  we  find  an  extraordinarily  rapid  suc- 
cession of  generations.  In  the  time  required  for  the  pro- 
duction of  one  generation  of  a  larger  higher  animal,  the 
lower  type  has  had  many  generations  and  has  produced 
an  enormously  greater  weight  of  living  matter.  It  was 
this  that  led  Linnaeus  to  say  that  three  flies  consume  the 
carcass  of  a  horse  as  quickly  as  a  lion  ('  Tres  muscse  con- 
sumunt  cadaver  equi,  seque  cito  ac  leo  '). 

Huxley  calculated  that  if  the  descendants  of  a  single 
green-fly  all  survived  and  multiplied,  they  would  at  the  end 
of  one  summer  weigh  down  the  population  of  China.  The 
descendants  of  a  common  house-fly  would  in  the  same  time 
— six  generations  of  about  three  weeks  each — occupy  a 


132  THE  WONDER  OF  LIFE 

space  of  something  like  a  quarter  of  a  million  cubic  feet, 
allowing  200,000  flies  to  a  cubic  foot.  An  oyster  may  have 
sixty  million  eggs,  and  the  average  American  yield  is 
sixteen  millions.  If  all  the  progeny  of  one  oyster  survived 
and  multiplied,  and  so  on  till  there  were  great-great-grand- 
children, these  would  number  sixty-six  with  thirty-three 
noughts  after  it,  and  the  heap  of  shells  would  be  eight  times 
the  size  of  the  earth!  Of  course  none  of  these  things 
happen,  because  of  the  checks  imposed  by  the  struggle  for 
existence.  Yet  every  now  and  then,  as  man  knows  to  his 
cost,  a  removal  or  diminution  of  the  natural  checks  allows 
the  potential  productivity  to  assert  itself  for  a  short  time 
or  within  a  limited  area.  The  river  of  life  sometimes  does 
overflow  its  banks,  as  it  always  tends  to  do,  and  the  result- 
ing flood  is  called  a  plague.  But  one  plague  brings  another 
in  its  train,  as  in  Egypt  long  ago,  and  things  right  them- 
selves, usually  with  considerable  loss  in  the  process. 

The  large  African  land-snail  Achatina  fulica  was  intro- 
duced about  1900  into  central  Ceylon,  but  was  shortly  after- 
wards practically  exterminated.  A  couple  that  escaped 
destruction  were  carried  down  some  years  afterwards  to  the 
low  country.  '  Here  they  increased  to  such  an  amazing 
extent,  over  an  area  of  about  five  square  miles,  that 
their  numbers  were  to  be  reckoned  by  millions,  no  fewer 
than  227  being  counted  in  a  cluster  on  the  stem  of  a 
cocoa-nut  palm  in  a  length  of  about  6  feet '.  Luckily  little 
or  no  damage  has  been  done,  as  the  snail  acts  as  a  scavenger. 
The  adults  are  attacked  by  a  terrapin  of  the  genus  Nicoria, 
the  young  stages  have  many  enemies,  and  the  early 
exuberance  of  multiplication  is  now  being  checked. 

On  the  night  before  the  new  or  full  moon  in  the  middle 
or  latter  half  of  December  there  occurs  the  remarkable 


THE  INSURGENCE  OF  LIFE  133 

swarming  of  the  Japanese  Palolo  worm.  It  invariably 
takes  place  about  midnight  just  after  flood-tide.  At  1  a.m., 
Akira  Izuka  relates,  the  worms  '  covered  the  whole 
water  as  with  a  sheet '  and  were  thick  down  to  a  depth  of 
a  fathom.  By  2.15  a.m.  there  was  not  a  single  worm  to 
be  seen  ;  the  reproductive  orgasm  was  over.  The  pheno- 
menon appears  to  us  to  be  a  dramatic  instance  of  the 
abundance  of  life,  of  the  crisis-nature  of  reproduction,  and 
of  the  precise  way  in  which  internal  rhythms  may  be 
related  to  external  periodicities. 

Dr.  Th.  Mortensen  has  called  attention  to  the  extra- 
ordinary fecundity  of  the  starfish  Luidia  ciliaris,  which  is 
well  known  in  British  seas.  The  beautiful  red  ovaries  are 
arranged  in  a  double  series  in  each  arm  or  ray — 300  in  an 
arm  30  cm.  long.  As  the  species  is  seven-armed  a  complete 
female  of  that  size,  which  is  nearly  the  average,  has  2,100 
ovaries.  In  one  ovary  there  are  at  least  300,000  eggs, 
probably  nearer  half  a  million.  As  the  ovaries  are  smaller 
towards  the  tip  of  the  arm,  it  may  be  just  to  take  the  mean 
number  of  eggs  per  ovary  at  100,000,  and  the  number  of 
ovaries  may  be  reduced  to  2,000 ;  this  gives  the  number 
of  eggs  in  a  grown  female  at  no  less  than  200  millions. 
Yet  the  larvae  are  relatively  rare  and  the  adults  are  far 
from  common.  '  What  a  waste  of  eggs  must  here  take 
place  !  ' 

Professor  Lorande  Loss  Woodruff,  of  Yale,  who  has 
devoted  many  years  to  the  experimental  study  of  the 
slipper  animalcule  (Paramoecium),  gives  a  very  interesting 
account  of  a  five-year  pedigreed  race.  On  May  1,  1907,  he 
started  with  a  '  wild '  Paramoecium  aurelia,  isolated  from 
an  aquarium.  When  it  had  produced  four  individuals 
by  division,  these  were  isolated  to  form  the  ancestors  of 


134  THE  WONDER  OF  LIFE 

four  lines.  The  pedigreed  culture  was  maintained  by 
taking  a  specimen  practically  every  day  from  each  of  these 
lines  up  to  May  1,  1912.  This  facilitated  an  accurate 
record  of  the  number  of  generations  attained,  and  it 
also  precluded  the  possibility  of  conjugation  taking  place, 
for  this  process  of  incipient  sexual  union  does  not  occur 
between  forms  which  are  all  descended  from  one  by 
repeated  asexual  fission. 

In  the  five  years  there  were  three  thousand  and  twenty- 
nine  generations,  four  hundred  and  fifty-two  in  the  first, 
six  hundred  and  ninety  in  the  second,  six  hundred  and 
thirteen  in  the  third,  six  hundred  and  twelve  in  the  fourth, 
and  six  hundred  and  sixty-two  in  the  fifth.  The  mean 
rate  of  division  was  over  three  divisions  in  forty-eight 
hours. 

The  slipper-animalcules  were  as  healthy  in  1912  as  in 
1907.  They  had  given  evidence  of  the  potentiality  of 
producing  a  volume  of  protoplasm  approximately  equal  to 
10,000  times  the  volume  of  the  earth  !  The  experiments 
illustrate  admirably  the  extraordinary  self-reproducing 
capacity  of  living  matter.  They  also  seem  to  show  that 
given  an  ideally  favourable  environment  there  is  no 
need  for  the  occurrence  of  conjugation  and  no  reason  for 
senescence.  The  slipper-animalcules  preserve  the  secret 
of  eternal  youth. 

FILLING  EVERY  NICHE 

Fauna  of  a  Stone. — No  one  who  has  made  the  experi- 
ment will  forget  the  lesson  learned  by  making  a  census 
of  the  population  of  a  single  creviced  stone  brought  up  by 
the  dredge.  Molluscs,  Crustaceans,  Worms,  Echinoderms, 
Zoophytes,  Sponges,  Protozoa,  and  other  groups  may  be 


THE   INSURGENCE  OF  LIFE  135 

all  represented.  In  a  report  on  the  Bryozoa  collected  on 
the  Clare  Island  Survey,  Mr.  A.  R.  Nicholls  notices  that 
from  one  stone  no  fewer  than  fourteen  different  species 
of  these  colonial  '  moss-animals  '  were  obtained.  A  small 
stone  bore  eleven  species  of  the  same  class  !  We  see  the 
same  filling  of  every  corner  all  the  world  over. 

Red  Snow. — The  striking  phenomenon  of  Red  Snow 
was  known  to  the  ancients  and  is  mentioned  by  Aristotle. 
It  occurs  all  the  world  over  and  affords  a  good  illustration 
of  what  we  call  insurgence.  It  seems  to  be  most  abundant 
in  the  Far  North  and  Sir  John  Ross  described  the  '  Crim- 
son Cliffs  '  of  Greenland  as  extending  for  miles  !  The  ordin- 
ary '  red  snow  '  is  due  to  swarms  of  a  Flagellate  Infusorian, 
Sphcerella  (or  Protococcus)  nivalis,  sometimes  claimed  by 
the  botanists,  but  there  are  sometimes  red  animals  of  higher 
degree,  namely  Rotifers,  Water-Bears,  Mites,  associated 
with  it — forming  a  '  Red  Snow  '  fauna.  The  facts  have 
been  recently  summed  up  by  Mr.  James  Murray,  who  was 
zoologist  on  Sir  Ernest  Shackle  ton's  Antarctic  Expedition. 
He  found  abundance  of  a  red  Rotifer,  which  he  named 
Philodina  gregaria,  forming  conspicuous  blood-red  stains 
on  stones  at  the  margins  of  lakes,  and  increasing  with 
prodigious  rapidity.  It  lives  frozen  in  ice  for  years,  and 
resumes  activity  whenever  the  ice  melts.  Vogt  found  a 
related  species  (Philodina  roseola]  on  the  Alps  along  with 
the  Flagellate  '  red  snow  '  ;  Langerheim  found  the  same 
association  in  Ecuador.  The  red  colour  of  both  Alpine  and 
Polar  Rotifers  is  confined  to  the  stomach,  which  looks 
as  if  the  colour  were  due  to  the  Rotifers  making  meals  of 
the  Flagellates.  Mr.  Murray  notices  in  addition  that  M. 
Gain  of  the  Charcot  Antarctic  Expedition  found  red  mites 
along  with  the  red  snow,  and  that  Ehrenberg  long  ago 


136  THE  WONDER  OF  LIFE 

found  a  red  water-bear  and  a  red  Eotifer  (Callidina  scar- 
latina] among  snow  on  Monte  Rosa  at  a  height  of  11,138 
feet,  which  is  another  good  instance  of  the  insurgence  of  life. 

Brine  Shrimps. — The  pretty  little  brine-shrimp 
(Artemia  salina)  that  used  to  occur  in  British  salterns,  and 
has  a  widespread  distribution  from  the  Great  Salt  Lake 
of  Utah  to  Central  Asia,  is  famous  in  several  ways,  and 
notably  because  it  can  live  in  water  with  as  much  as  27 
per  cent,  of  dissolved  salts,  yet  occurs,  though  rarely,  in  fresh 
water.  It  is  usually  about  half  an  inch  long  and  has  a  pale 
reddish  colour,  due,  as  Sir  Ray  Lankester  first  showed,  to 
the  presence  in  the  body  fluids  of  haemoglobin — the  char- 
acteristic vertebrate  blood  pigment  which  is  somewhat 
rare  in  Invertebrates.  In  some  places  the  colonies  seem 
to  be  altogether  female,  and  parthenogenesis  obtains,  the 
eggs  developing  without  being  fertilized.  In  other  localities 
males  are  common  and  reproduction  takes  place  by  means 
of  fertilized  eggs.  Sometimes  the  Brine  Shrimp  is  vivi- 
parous, the  eggs  hatching  within  the  mother's  brood-sac  and 
giving  rise  to  microscopic  larvae  (Nauplii)  with  three  pairs  of 
limbs  and  an  unpaired  eye.  Variable  in  its  reproduction, 
the  Brine- Shrimp  is  variable  also  in  its  form,  especially  as 
regards  the  end-lobes  of  the  tail  and  the  bristles  they  bear. 
Perhaps  this  is  correlated  with  the  chemical  diversity  of 
the  habitats  frequented.  The  eggs  can  survive  being  dried 
and  may  be  blown  about  by  the  wind  or  carried  on  the  feet 
of  birds  from  one  salt  pond  to  another.  We  have  already 
referred  to  their  occurrence  In  Tidman's  Sea-Salt. 

A  Hazardous  Home. — One  knows  the  narrow  shelves 
high  up  on  the  Alps,  which,  for  part  of  the  year  at  least, 
are  the  homes  of  men,  women,  and  children ;  one  knows 
the  narrow  ledges  on  the  precipitous  Bird-bergs  where 


THE  INSURGENCE  OF  LIFE  137 

kittiwakes  and  guillemots  and  many  other  sea-birds  have 
their  summer  quarters  and  bring  up  their  family  ;  one  has 
seen  the  water-snails  browsing  nonchalantly  on  the  minute 
vegetation  on  the  stones  of  the  Niagara  River  within  a  few 
yards  of  the  Falls  ;  but  are  any  of  these  habitats  so  remark- 
able as  that  of  a  spider  that  lives  inside  one  of  the  Pitcher- 
plants  ?  In  that  notorious  lure  for  insects,  with  its  very 
slippery  internal  surface,  and  noxious  dungeon  full  of 
rottenness,  the  spider  lives  and  thrives.  Forestalling  the 
plant,  it  catches  some  of  the  insect  victims  as  they  slip 
down  the  facilis  descensus  Averni  and  sucks  their  juices, 
letting  the  dry  corpses  tumble  into  the  pit.  This  is  certainly 
one  of  the  strangest  of  habitats.  They  say,  moreover,  that 
when  an  insectivorous  bird — aware  of  the  plant's  device 
— arrives  on  the  scene  and  proceeds  to  break  down  the 
prison-walls,  the  spider  plunges  into  the  foul  fluid  in  the 
foot  of  the  pitcher,  is  able  to  survive  suffocation  for  a 
time,  and  eventually  escapes  as  the  tearing-up  is  accom- 
plished. 

Larvae  of  Flies. — There  is  no  parallel  in  the  rest  of  the 
animal  kingdom  to  the  variety  of  habit  and  habitat  that 
is  illustrated  by  the  larvae  of  Dipterous  insects.  Mr.  J.  C. 
Hamon  found  larval  Stratiomyidse  in  a  hot  spring  in 
Wyoming,  where  he  could  not  keep  his  hand  immersed,  and 
others  occur  in  brine.  Some  are  found  in  the  rushing 
torrent,  and  others  in  the  rain-water  barrel.  Some  are 
found  in  the  midst  of  filth,  and  others  cannot  endure  the 
least  contamination.  Some  are  parasitic,  and  others  have 
an  extremely  active  free  life.  Let  us  take  as  an  instance 
in  more  detail  the  larva  of  Simulium  reptans,  a  British 
representative  of  the  buffalo-gnats.  The  adult  fly  bites 
hard  and  is  irritating  to  man,  but  it  is  not  to  be  compared 


138  THE  WONDER  OF  LIFE 

with  other  species  which  do  serious  damage  among  herds 
of  cattle  in  the  valley  of  the  Danube  and  in  the  United 
States. 

The  larva  of  Simulium  reptans  lives  in  rushing  water, 
holding  on  to  water-buttercup  and  the  like  by  a  clawed 
sucker  at  the  posterior  end  of  the  body.  It  has  a  similar 
sucker  on  the  thorax,  and  it  seems  to  use  this  one  when  it 
moves  about  on  the  weed.  Another  safeguard  is  to  be 
found  in  its  ability  to  exude  an  attaching  thread  from  its 
salivary  glands.  It  is  about  12  mm.  long,  of  a  greenish- 
black  colour,  and  it  is  continually  wafting  food  into  its 
mouth  by  the  action  of  two  pairs  of  beautiful  sweepers. 
The  larva  pupates  in  a  silken  pouch  or  cocoon  fixed  to  the 
weed,  and  showing  a  pair  of  projecting  respiratory  processes. 
Professor  Miall  describes  the  emergence  of  the  winged  fly 
from  the  sub-aquatic  cradle,  and  how  it  is  wafted  up  to 
its  appropriate  element  as  If  inside  a  large  water-bubble 
— an  ingeniously  simple  device  ! 

Nets  of  Caddis  Larvae. — C.  Wesenberg-Lund  has 
given  a  very  interesting  account  of  the  peculiar  nets  made 
by  the  larvae  of  some  of  the  Caddis-flies  of  lakes  and 
streams.  They  serve  for  the  capture  of  the  drifting  plank- 
ton. Some  are  trumpet- shaped,  up  to  four  inches  in 
length,  with  the  mouth  always  upstream.  They  are  bluish- 
green  in  summer  because  of  the  Algae  on  the  threads, 
and  brownish  in  winter  because  of  the  diatoms.  Other 
nets  are  flat,  with  an  aperture  in  the  centre  leading  down 
into  a  tunnel  beneath  a  stone ;  others  are  like  swallows' 
nests  and  are  fastened  in  large  numbers  to  the  vertical 
banks  ;  others  are  funnel-shaped  and  fixed  to  the  pond- 
weed  leaves  ;  others  make  chains  of  baskets  out  of  duck 
weed  leaves  and  spin  a  web  on  the  front  of  each.  The 


FIG.  36— Nets  of  larval  Caddis-Flies.     (After  Wesenberg-Lund.)      I.  Larva  of  Holocentropus 
dubius.     III.  Its  snare-nest.     II.  Snare-nest  of  Neureclipsis  bimaculata. 


THE   INSURGENCE  OF  LIFE  139 

spinning  larvae  are  campodeiform  in  type,  that  is,  not  so 
worm-like  as  ordinary  caddis-worms,  and  they  differ  also 
in  being  very  sedentary  and  practically  carnivorous.  The 
author  writes  (in  1911)  :  'It  seems  strange  that  until  now 
we  have  hardly  had  any  idea  at  all  as  to  the  spinning  powers 
of  these  animals  ;  as  the  spider  spins  its  web  above  ground, 
and  lies  in  wait  for  the  winged  insects  and  the  flying  plank- 
ton of  the  air,  so  the  campodeoid  larva  constructs  its  net, 
lurking  for  the  small  animals  and  floating  plankton  of 
lakes  and  water- courses.' 

Strange  Habitats. — In  hunting  for  earthworms  one  does 
not  naturally  look  up  a  tree,  but  Dr.  Robert  Stager  has 
shown  that  it  is  a  useful  plan  to  search  in  unlikely  places. 
In  exploring  on  the  Alps  he  investigated  the  mossy  cushions 
which  often  flourish  on  the  stem  and  branches  of  the 
sycamore  and  bear  ferns  and  various  flowering  plants.  In 
that  strange  habitat  he  found  four  different  species  of 
earthworm.  Others  occurred  in  the  familiar  cushions 
formed  on  almost  bare  rock  by  plants  like  Dryas  octopetala, 
Silene  acaulis,  and  Gypsophila  repens.  Again  we  have  illustra- 
tion of  the  way  life  insinuates  itself  into  every  vacant  niche. 

Another  strange  habitat  is  that  of  an  '  unsalamander-like 
salamander '  (Autodax  lugubris)  which  lives  up  trees 
(Quercus  agrifolia).  W.  E.  Ritter  found  them  in  holes  at 
a  height  of  30  feet,  sometimes  as  many  as  a  dozen  in  one 
hole,  representing  perhaps  a  family.  Most  of  the  cavities 
occupied  had  very  narrow  openings.  The  eggs  are  hung 
in  clusters  from  an  overhanging  surface,  each  egg  on  a  little 
string  of  its  own,  and  both  sexes  look  after  them.  Most 
Amphibians  are  gentle  creatures,  but  these  Salamanders 
are  very  ready  to  show  fight  in  defence  of  their  eggs  or 
themselves,  and  they  have  very  large  teeth. 


140  THE  WONDER  OF  LIFE 

Another  series  of  strange  habitats  has  been  found  in  the 
burrows  made  by  moles  and  hamsters  and  other  mammals 
of  similar  habit.  There  are,  of  course,  accidental  co- 
tenants  ;  and  there  are  others  which  though  often  found  in 
burrows  occur  elsewhere  as  well ;  and  there  are  parasites 
belonging  to  the  burrowing  mammals.  But  after  these 
are  taken  account  of  there  remains  a  distinct  burrow- fauna, 
just  as  there  is  a  distinct  cavern-fauna.  Thus  L.  Falcoz 
mentions  the  Staphylinid  beetles,  Heterops  prcevia, 
Oxypoda  longipes,  and  Aleochara  spadicea  as  good  illus- 
trations of  the  fauna  of  moles'  nests. 

Many  beetles  visit  nests  casually  for  pickings ;  others 
are  frequenters  of  nests  but  of  other  suitable  places  as 
well ;  there  is  a  third  lot  of  exclusively  '  nidicolous ' 
Coleoptera,  and  the  list  of  these  drawn  up  by  Bickhardt 
in  1911  came  to  twenty-eight.  Eighteen  of  these  are 
confined  to  the  homes  of  mammals,  such  as  mole,  hamster, 
mouse,  and  rabbit ;  seven  are  confined  to  the  nests  of 
birds,  such  as  dove,  sand-martin,  owl,  and  woodpecker ; 
three  are  found  associated  with  both  birds  and  mammals. 

A  curious  refuge  is  that  of  the  rare  sea-otter — on  the 
great  beds  of  kelp  seaweed  (Macrocystis]  which  fringe  the 
rocky  coast  of  the  North  Pacific,  among  the  Aleutian  and 
Kurile  Islands.  We  read  that  '  these  great  kelp  beds 
make  calm  water,  though  the  surf  be  roaring  and  breaking 
just  outside,  and  are  dense  enough  for  the  otters  to  lie 
upon.'  In  the  middle  of  the  nineteenth  century  the  sea- 
otter  was  still  comparatively  plentiful  all  round  the  North 
Pacific  coast,  now  it  is  hardly  to  be  seen  even  by  the 
exploring  naturalist.  It  is  interesting  in  its  adaptations 
for  aquatic  life — the  hind  feet  being  suited  only  for  swim- 
ming ;  in  the  adaptation  of  its  back  teeth  for  crunching  crabs, 


THE   INSURGENCE  OF   LIFE  141 

molluscs,  and  sea-urchins — the  crowns  being  smooth  and 
rounded ;  and  in  the  care  for  the  pup  which  the  mother 
shows, — dandling  it,  and  diving  with  it. 

The  Penelope  Spider. — Not  only  do  living  creatures 
fill  every  cranny  in  the  rock-pool,  every  nook  in  the 
grassy  bank,  they  take  advantage  of  every  niche  of 
opportunity.  The  illustrations  are  world- wide.  Professor 
Goeldi  gives  us  one  from  a  garden  near  Para.  The  time  is 
long  before  dawn  and  the  chief  actor  is  a  spider,  spinning 
in  the  dim  light.  Before  the  sun  rises  her  web  is  finished, 
and  it  serves  to  catch  the  winged  male  scale-insects  in 
their  early  morning  nutter.  But  as  the  sun  rises,  the 
spinner  grows  restless ;  she  dislikes  the  light  of  day,  just 
as  does  the  poacher  who  has  by  night  spread  in  the  field 
his  net  for  birds.  So,  at  the  dawning,  the  spider  draws 
her  net  together  with  its  quivering  delicate  captives,  and 
retires  into  the  shade  to  investigate  the  catch.  It  was  only 
by  staying  up  all  night  in  the  garden  that  Professor  Goeldi's 
son  discovered  the  secret  of  this  light-avoiding  spider  whose 
web  disappears  with  the  morning  dew.  It  is  a  mode  of 
bread-winning  that  fills  a  curious  niche  of  opportunity. 
Penelope-like,  the  spinner  makes  and  unmakes  her  web 
each  day,  but  not  without  effective  results  to  man  (by 
destroying  the  injurious  scale- insects)  as  well  as  to  herself. 

Successive  Waves  of  Life. — The  pressing  insurgence 
of  life  which  is  illustrated  by  the  way  in  which  organisms 
fill  every  niche — even  the  least  inviting — is  illustrated  in 
quite  another  way  when  we  observe  a  sequence  of  possessors 
passing  like  waves  over  a  particular  environment.  When 
one  horde  has  made  an  area  uninhabitable  for  itself  by 
exhausting  the  food-supply,  there  may  come  another  able 
to  cut  even  closer  to  the  bone.  We  see  this  in  a  very 


142  THE  WONDER  OF  LIFE 

striking  way  in  the  sequence  of  animal  and  plant  life  in  a 
'  hay  infusion  ' — one  form  after  another  rising  into  domin- 
ance and  then  disappearing.  In  this  connexion  Professor 
L.  L.  Woodruff  of  Yale  has  shown  that  the  slipper-animal- 
cule (Paramoecium),  excretes  substances  which  are  poisonous 
to  itself  when  they  accumulate  in  a  limited  environment. 
Thus  when  Paramcecium  reaches  its  maximum,  the  be- 
ginning of  the  end  is  not  far  off. 

DIFFICULT  CONDITIONS 

Who  has  not  been  impressed  by  the  way  in  which  living 
creatures  triumph  over  the  most  unpromising  circum- 
stances ?  We  went  up  the  other  day  to  a  well-known  minor 
pass  in  the  Alps  where  we  were  getting  near  the  lasting 
snows  and  the  bare  inhospitable  rocks.  It  seemed  ill-suited 
to  be  a  home,  but  what  impressed  us  most,  after  the  view  of 
the  mountains,  was  the  abundant  insurgent  life ;  we  felt 
what  Bergson  calls  the  elan,  the  spring,  the  impetus  that  is 
characteristic  of  life.  Not  only  were  there  many  beautiful 
flowers  coming  up  even  at  the  thinned  edges  of  the  snow 
mantle,  but  there  was  quite  a  rich  insect  life.  Conspicuous, 
too,  were  the  large,  white-bellied  Alpine  swifts,  perhaps  the 
most  rapid  of  birds,  continually  swirling  about,  all  in  silence, 
in  the  cold  air  :  emblems  of  insurgent  life.  Shy  marmots 
whistled  from  among  the  rocks.  Flocks  of  white  moths 
floated  up  in  the  mist,  rising  like  the  souls  of  animals  that 
had  died  far  below.  We  felt  the  insurgent  indomitable 
quality  of  life. 

Antarctic  Shores. — On  Sir  Ernest  Shackleton's  Antarctic 
Expedition  several  collections  were  made  at  Cape  Royds 
(77°  32'  S.),  at  first  sight  a  most  unpromising  locality. 
On  the  shore  there  was  no  vestige  of  life ;  nothing  but 


THE   INSURGENCE  OF  LIFE  143 

funereal  black  sand  when  the  '  foot-ice  '  was  gone.  Inshore 
there  was  black  lava,  showing  no  vegetation  higher  than 
mosses,  and  very  little  of  them.  Even  the  lichenous  tripe 
de  roche,  familiar  in  books  of  Arctic  exploration  for  its 
role  in  staving  off  starvation,  was  scarcely  so  abundant 
as  to  fulfil  the  same  life-saving  role  in  the  Antarctic. 
Ice  covered  the  sea  ;  ice — fifteen  feet  of  it — covered  the 
little  lakes.  Could  any  faunistic  outlook  have  been  more 
unprepossessing  ? 

But  the  reality  was  very  different  from  the  appearance. 
Mr.  James  Murray  and  the  other  workers  under  his  guid- 
ance wasted  no  time  in  bemoaning  the  absence  of  faunistic 
amenities.  They  made  holes  in  the  ice,  which  the  Weddell 
seals  helped  to  keep  open,  and  set  traps  which  yielded 
molluscs,  crustaceans,  and  worms.  They  managed  to  haul 
a  dredge  from  one  hole  to  another,  and  got  sponges,  sea- 
anemones,  alcyonarians,  starfishes,  crustaceans,  and 
molluscs.  They  cut  down  through  fifteen  feet  of  ice  in  the 
small  inland  lakes,  and  reached  a  floor  of  '  foliaceous  vege- 
tation ', — and  a  rich  micro-fauna  and  micro-flora.  There 
were  abundant  Rotifers,  especially  of  two  new  viviparous 
species,  which  subsequent  experiment  showed  to  be  able 
to  withstand  all  sorts  of  changes  of  temperature.  There 
were  '  water-bears,'  or  Tardigrades,  and  water-mites,  and 
two  species  of  '  water-fleas  ',  besides  thread- worms,  In- 
fusorians,  and  two  kinds  of  Rhizopods.  Here  then  in  the 
collecting  at  Cape  Royds  we  get  another  illustration  of  the 
insurgence  of  life.  We  see  life  persistent  and  intrusive — 
spreading  everywhere,  insinuating  itself,  adapting  itself ; 
resisting  everything,  defying  everything,  surviving  every- 
thing. 

Desert-Plants. — A  well-known  adaptation  to  difficult 


144  THE   WONDER  OF  LIFE 

conditions  is  exhibited  by  desert  plants  which  store  water. 
They  have  a  relatively  large  root-system  which  enables 
them  to  make  the  most  of  any  available  supply.  F.  V. 
Coville  found  in  the  Mohave  Desert,  California,  a  branching 
cactus  (Opuntia  echinocarpa),  19  inches  high,  which  had  a 
network  of  roots  extending  over  an  area  18  feet  in  diameter. 
These  roots  were  2  to  4  inches  below  the  surface,  suited 
therefore  for  utilizing  a  downpour.  Some  desert  plants  send 
their  roots  deep,  and  Professor  R.  H.  Forbes  has  described 
an  acacia  of  Arizona  which  has  a  double  root-system,  one 
for  absorption  near  the  surface,  and  the  other  for  searching 
deeply. 

The  collecting  surface  is  great,  and  the  losing  green  surface 
is  small ;  the  whole  plant,  as  in  many  cactuses,  may  be 
like  a  ball  or  barrel  and  without  leaves.  The  structure  of 
the  cuticle  and  even  of  the  transpiration  pores  is  adapted 
to  lose  as  little  as  possible,  and  the  interior  of  the  plant 
consists  chiefly  of  water-storage  cells,  so  that  as  much  as 
96  per  cent,  of  water  can  be  collected.  The  plant  becomes  a 
tank  and  the  water  is  often  quite  drinkable.  A  Barrel- 
Cactus  or  Bisnago  (Echinocactus  emoryi)  studied  by  Coville 
yielded  3  quarts  of  water  from  about  8  inches  of  a  plant 
about  a  yard  high  and  20  inches  in  diameter.  It  may  be 
further  noted  that  the  Bisnago  is  effectively  protected 
against  grazing  animals  by  the  impenetrable  armour  of 
hooked  and  rigid  spines,  and  another  notable  feature  is  the 
fluted  surface  which  allows  it  to  expand  and  contract 
without  cracking.  When  we  think  of  the  root-system, 
the  leaflessness,  the  barrel-shape,  the  skin,  the  water-cells, 
the  spines,  the  fluting — we  realize  what  a  bundle  of  adapta- 
tions this  desert  plant  is,  and  many  other  slightly  different 
examples  might  be  given.  Although  the  Barrel-Cactus 


THE   INSURGENCE  OF  LIFE  145 

seems  to  be  peculiarly  safe  (except  from  man,  who  some- 
times taps  it),  there  are  many  desert  plants  whose  stores 
form  the  only  water  supply  of  not  a  few  of  the  desert 
animals. 

Rock -Borers. — Life's  characteristic  filling  of  every 
niche  leads  to  extraordinary  modes  of  life.  Instead  of 
seeking  a  life  of  ease,  many  animals  attempt  what 
seems  impossible,  and  achieve  it.  Take  the  simple  case 
of  boring  bivalves,  like  the  Pholads,  which  work  their  way 
into  hard  rock.  According  to  one  theory,  the  boring  is  at 
least  partly  due  to  an  acid  secretion  ;  according  to  another 
view  it  is  mainly  accomplished  by  mechanical  means.  Miss 
B.  Lindsay  made  a  very  careful  study  of  Zirphcea  (Pholas) 
crispata  and  Saxicava  rugosa  at  St.  Andrews,  and  came  to 
the  conclusion  that  the  boring  is  in  these  cases  entirely 
mechanical.  The  Pholas  works  in  two  ways — sucking  and 
scraping.  '  It  might  be  described  as  a  combination  of  a 
nutmeg-grater  and  a  vacuum- cleaner '.  The  foot  is 
extruded ;  a  wide  gap  appears  between  the  foot  and  the 
mantle ;  the  mantle  becomes  fully  extruded,  and  then 
rotatory  movements  begin.  An  interesting  detail  is  that 
the  shells  consist  of  aragonite,  which  is  harder  than  the 
usual  calcite,  and  this  must  help  a  little  in  the  process  of 
boring,  which  remains,  however,  when  all  is  said,  a  very 
remarkable  performance. 

Climbing  Fishes. — There  is  a  well-known  tropical  fish, 
Periophthalmus,  which,  like  its  relative  Boleophthalmus, 
spends  hour  after  hour  out  of  water,  squatting  on  the  mud 
by  the  sides  of  the  estuaries,  or  even  climbing  up  on  the 
roots  of  the  mangrove  trees.  But  such  climbing  powers  as 
Periophthalmus  possesses  are  far  surpassed  by  those  of  a 
catfish,  Arges  marmomtus,  which  lives  in  the  torrential 


146  THE  WONDER  OF  LIFE 

rivers  of  the  Andes,  where  there  is  a  rapid  succession  of 
falls,  cascades,  and  potholes.  Under  usual  conditions 
Arges  is  a  clumsy  and  awkward  swimmer,  but  for  creeping 
and  climbing  in  the  torrents  it  is  wonderfully  adapted.  It 
anchors  itself  by  its  suctorial  mouth,  and  works  itself  up- 
stream with  the  help  of  a  ventral  bony  plate  bearing  the 
ventral  fins  and  equipped  with  strong  muscles  which  move 
it  backwards  and  forwards.  The  plate  is  studded  with 
small  sharp  teeth  pointing  backwards.  These  catfishes 
climb  up  the  smooth  water- worn  surfaces  of  deep  potholes, 
and  have  been  known  to  ascend  eighteen  feet  without  a  slip 
or  fall. 

Terrestrial  Animals  Under  Water.— On  the  Mediter- 
ranean shore  among  the  calcareous  Algae,  Racovitza  found 
a  marine  spider,  which  Louis  Fage  has  described  under  the 
title  Desidiopsis  racovitzai.  It  lives  in  crevices,  in  burrows 
(of  Lithodomus),  in  empty  shells  (of  Vermetus),  and  keeps 
the  water  out  more  or  less  by  spinning  threads  across  the 
entrance  to  its  retreat.  There  is  no  tide  to  contend  with, 
but  it  is  a  strange  abode  for  a  terrestrial  animal.  Unlike 
the  freshwater  spider,  it  cannot  swim.  It  can  remain 
for  a  long  time  under  water,  but  has  to  return  to  dry 
land  periodically  to  get  a  supply  of  air,  which  is  entangled 
about  the  posterior  body.  What  the  creature  feeds  on  is 
uncertain. 

A  species  of  mite,  Eryihrceus  passerinii,  belonging  to  a 
terrestrial  stock,  is  known  to  live  in  the  crevices  of  the  sea- 
shore rocks,  and  to  be  able  to  withstand  prolonged  immer- 
sion. It  utilizes  the  air  imprisoned  in  the  capillary  passages 
in  the  cracks  of  the  rocks.  A  primitive  wingless  insect, 
Anurida  maritime/,,  which  has  been  carefully  studied  by 
Imms,  lives  habitually  among  the  sea-shore  rocks.  When 


THE   INSURGENCE   OF  LIFE  147 

the  tide  rises  it  retreats  far  into  crevices  or  into  the 
sand.  The  whitish  hairs  on  its  body  hold  a  supply  of  air, 
which  may  last  for  4£  days.  There  are  also  two  British 
parasitic  gall-flies  that  occur  at  high-water  mark  among  the 
sea-weed  of  the  jetsam. 

Aquatic  Insects. — The  adaptations  of  aquatic  insects 
form  a  well-nigh  inexhaustible  theme.  Let  us  take  a 
couple  of  instances  from  Dr.  Boring's  account  of  the  larvae 
of  the  Donaciinae,  a  sub-family  of  the  Chrysomelids,  or  leaf- 
beetles.  The  larvae  puncture  the  roots  of  water-plants, 
such  as  pond- weed  and  Sparganum,  and  feed  on  the  exu- 
ding sap.  In  making  the  hole,  by  means  of  the  cutting 
mandibles,  the  neatest  possible  contrivance  comes  into 
operation.  The  first  segment  of  the  thorax  slips  forward 
against  the  plant  and  within  the  water-tight  compartment 
thus  formed,  the  head  works  freely  and  the  sap  is  kept 
from  adulteration  with  water  and  debris. 

The  adaptation  for  breathing  is  not  less  striking,  for  the 
larvae  manage  to  tap  the  stores  of  air  in  the  intercellular 
spaces  of  water  plants.  A  hooked  breathing  pore  or 
spiracle  at  the  end  of  the  abdomen  is  plunged  into  the 
tissue  of  the  plant  and  the  air  finds  its  way  (in  a  somewhat 
intricate  fashion)  into  the  breathing-tubes  or  trachese  of 
the  insect.  Similarly,  after  the  larva  has  enveloped  itself 
in  a  secreted  cocoon,  it  actually  bites  a  hole,  or  more 
than  one,  at  the  bottom  and  establishes  connexion  with 
the  air  spaces  of  the  root  to  which  it  is  attached.  In  this 
way  it  secures  a  supply  of  air  during  its  pupal  period  ! 

Against  the  Grain. — It  seems  to  be  part  of  the 
Amphibian  constitution  to  have  an  antipathy  to  salt — 
a  small  quantity  being  often  fatal.  Referring  to  the  absence 
of  Amphibians  from  strictly  oceanic  islands  Darwin  pointed 


148  THE  WONDER   OF  LIFE 

out  that  they  throve  particularly  well  when  artificially 
introduced,  as  into  Madeira,  the  Azores,  and  Mauritius, 
'  but  as  these  animals  and  their  spawn  are  immediately 
killed  (with  the  exception,  as  far  as  known,  of  one  Indian 
species)  by  sea- water,  there  would  be  great  difficulty  in 
their  transportal  across  the  sea,  and  therefore  we  can  see 
why  they  do  not  exist  on  strictly  oceanic  islands  '.  They 
could  not  be  transported  on  trees  and  the  like,  as  some 
animals  have  been,  without  fatal  drenching.  Darwin 
makes  mention  of  an  exception,  and  we  have  recently 
(1911)  had  a  circumstantial  account  by  Mr.  A.  S.  Pearse 
of  sea-shore  frogs  at  Manila.  He  quotes  Dr.  Gadow's 
words,  '  Common  salt  is  poison  to  the  Amphibia ;  even 
a  solution  of  1  per  cent,  prevents  the  development  of  the 
larvae  ',  and  then  reports  that  he  saw  little  frogs  of  the 
genus  Eana  hopping  about  on  the  flats  of  an  estero,  or  tidal 
creek,  opening  into  Manila  Bay.  Two  holes  made  by  the 
crab  Sesarma  bidens  were  seen  to  be  full  of  wriggling  tad- 
poles newly  hatched.  Samples  of  water  from  a  pool  with 
tadpoles  on  the  edge  of  the  creek  were  analysed,  and  it  was 
found  that  the  tadpoles  were  developing  in  slightly  diluted 
sea-water,  containing  as  much  as  2  per  cent,  of  sodium 
chloride.  It  seems,  then,  that  both  tadpoles  and  frogs  can 
stand  much  more  than  a  grain  of  salt. 

Audacity. — There  is  sometimes  what  we  may  venture 
to  call  sheer  audacity  in  the  things  animals  do  and  succeed 
in  doing.  Taking  such  a  serious  matter  as  the  disposal  of 
the  eggs  in  birds,  we  find,  of  course,  all  manner  of  careful 
nests  and  secure  hiding-places  and  safe  sites,  but  we  also 
find  sheer  audacity.  We  do  not  refer  to  the  often  reported 
cases  of  birds  nesting  inside  a  hat,  or  up  the  sleeve  of  a 
coat,  or  inside  an  unlit  station-lamp ;  for  while  a  few  of 


THE   INSURGENCE   OF   LIFE  149 

these  are  interesting,  the  majority  are  not,  since  we  are  apt 
to  forget  that  the  bird  does  not  know  what  hats  and  sleeves 
and  lamps  are.  In  many  cases,  moreover,  these  divergences 
prove  dismal  failures.  We  refer  rather  to  cases  like  the 
nesting  of  the  White  Tern  (Gygis  alba],  one  of  the  most 
interesting  and  beautiful  birds  of  Norfolk  Island  in  the 
Western  Pacific,  about  nine  hundred  and  fifty  miles  north- 
east from  Sydney.  The  bird  breeds  in  densely  wooded  gullies, 
and  it  lays  its  single  egg  in  a  knot-hole  or  any  slight  depres- 
sion on  a  more  or  less  horizontal  branch.  It  is  difficult  to 
think  of  any  more  hazardous  situation.  Mr.  A.  F.  Basset 
Hull  tells  us  that  '  the  sitting  bird  puffs  out  its  breast- 
feathers  so  as  to  completely  hide  the  egg,  depressing  its 
forked  tail  so  as  to  obtain  as  secure  a  hold  as  possible,  and 
sits  with  its  beak  pointing  into  the  eye  of  the  wind,  so  as 
to  offer  the  least  resistance  '.  Both  parents  share  in  the 
task  of  incubation,  and  we  are  not  surprised  to  learn  that 
they  show  great  caution  in  rising  and  settling.  It  is  the 
place  chosen  for  the  egg  that  chiefly  concerns  us,  but  we 
may  finish  Mr.  Hull's  interesting  story. 

'  I  saw  the  young  bird,  a  ball  of  black  down,  squatting 
unconcernedly  on  the  bare  limb  while  its  parents  were  away 
searching  for  food.  A  week  later  it  was  still  there,  and  had 
then  grown  nearly  as  large  as  its  mother,  but  it  was  still 
covered  with  the  black  down.  Its  mother  flew  up,  and 
straddled  over  it,  vainly  endeavouring  to  cover  it.  There  it 
sat  blinking  down  at  us,  like  a  black  piccaninny  in  the 
arms  of  a  white  nurse.' 

Tadpoles  of  a  Tree  Frog.— To  illustrate  a  cluster  of 
adaptations,  let  us  take  Dr.  W.  E.  Agar's  account  of  the 
nest  made  by  one  of  the  tree-frogs,  Phyllomedusa  sauvagii. 
The  adults  are  arboreal  in  their  habits,  and  yet  the  tadpoles 


150  THE  WONDER  OF  LIFE 

develop  in  the  water.  This  is,  so  to  speak,  arranged  for 
by  making  a  nest  among  the  leaves  of  bushes  overhanging 
the  pools,  and  this  nest  breaks  down  at  the  appropriate 
time,  allowing  the  newly  hatched  tadpoles  to  drop  into  the 
water.  A  number  of  leaves  are  held  together  by  a  deposit 
of  empty  gelatinous  egg-capsules,  such  as  we  sometimes  see 
in  ordinary  frog  spawn — spheres  of  jelly  without  an  egg 
inside.  It  appears  that  the  gelatinous  envelope  characteristic 
of  Amphibian  eggs  is  adhesive  when  it  is  not  in  contact 
with  water.  Thus  the  leaves  are  more  effectively  held 
together.  The  cavity  thus  formed  is  filled  up  with  a  mix- 
ture of  full  and  empty  egg-capsules,  and  then  there  is  a 
lid  of  empty  ones  on  the  top.  It  seems  that  the  empty 
capsules  not  only  keep  the  leaves  together  until  the  tadpoles 
are  ready  to  drop  out,  but  they  form  a  protective  shield 
lessening  the  risk  of  drying  up.  Dr.  Agar  observed  that 
there  was  least  mortality  in  the  more  perfect  nests,  so  that 
the  peculiarity  of  producing  empty  egg- capsules  and  the 
habit  of  using  them  is  just  such  a  peculiarity  as  would  be 
fostered  and  fixed  by  Natural  Selection. 

Defiance  of  Handicaps. — There  is  in  many  creatures 
an  extraordinary  defiance  of  circumstances — a  refusal  to 
admit  handicaps.  There  is  an  order  of  jellyfishes,  well 
represented  by  the  widely  distributed  green  and  blue 
Rhizostoma  pulmo,  in  which  the  mouth  is  normally  closed 
up  by  the  lips  so  that  only  minute  apertures  are  left  along 
the  lines  of  suture.  This  is  intelligible,  for  the  food  is 
microscopic  and  the  peculiarity  is  long  established.  But 
what  are  we  to  make  of  a  case  like  the  mouthless  carp 
described  by  J.  W.  Fehlmann,  which  lived  and  throve, 
though  its  food-canal  was  mouthless  and  blind.  That 
was  severe  handicapping,  but  the  fish  refused  to  die.  It 


THE  INSURGENCE  OF  LIFE  151 

lived  for  at  least  four  years,  feeding  as  well  as  breathing 
through  its  gill-clefts.  It  is  possible  that  the  carp  was  in 
part  sustained  by  nutritive  material  in  solution  in  the 
water,  but  there  were  numerous  mayfly  larvae,  crustaceans, 
pieces  of  plants  and  the  like  in  the  food-canal  which  must 
have  passed  in  by  the  breathing  apertures.  It  may  be 
recalled  that  according  to  some  speculative  anatomists  the 
present-day  mouth  of  backboned  animals  arose  from  the 
fusion  of  two  gill-clefts. 

In  any  case,  though  the  mouthless  carp  naturally  enough 
showed  no  trace  of  fat,  it  lived  for  at  least  four  years, 
and  that  is  the  sort  of  defiance  of  handicapping  which  we 
wish  to  illustrate. 

TENACITY  OP  LIFE 

The  toughness  of  some  animals  is  extraordinary,  and  is 
often  of  considerable  practical  importance  to  man,  for 
instance,  when  he  is  trying  to  rid  his  farm  or  garden  of 
injurious  insects.  They  are  so  difficult  to  kill.  The 
explanation  is  in  part  no  doubt  that  the  chitinous  cuticle 
is  very  impervious  and  resistant,  and  that  larvae  in  parti- 
cular are  able  to  close  their  mouth  and  breathing-pores. 
But  there  is  a  good  deal  left  to  explain.  A  very  careful 
worker,  L.  Bordas,  notes  that  he  immersed  potato  cater- 
pillars (Phtorimcea  opercuklla)  in  70  per  cent,  alcohol  for 
six  to  eight  hours,  and  found  them  still  able  to  contract 
the  body,  and  to  move  the  head  and  limbs  and  jaws ! 

The  larva  of  the  cheese-fly,  Piophila,  can  pass  right 
through  the  alimentary  canal  of  man  and  dog  without  being 
the  worse  for  it,  though  the  canal  may  be  worse  for  them,  as 
they  scratch  the  delicate  mucous  membrane  with  their 
oval  hooks.  Alessandri  put  some  for  sixteen  hours  in 


152  THE  WONDER  OF  LIFE 

70  per  cent,  alcohol  and  others  for  thirty  hours  in  petroleum, 
but  they  survived  it  all.  Such  is  the  toughness  of  some 
living  creatures. 

Some  of  the  statements  that  have  been  made  in  regard 
to  the  survival  of  complex  animals  after  prolonged  and 
severe  desiccation  require  to  be  revised.  In  some  cases,  at 
least,  the  creatures  themselves  die,  but  eggs  with  specially 
resistant  envelopes  ('  winter-  eggs ')  live  on  and  rapidly 
develop  when  there  is  a  restoration  of  favourable  conditions. 
Thus  D.  D.  Whitney  (1908)  found  that  out  of  forty-five 
different  species  of  Rotifers,  belonging  to  seventeen  families, 
only  two,  Philodina  roseola  and  P.  citrina,  could  success- 
fully withstand  desiccation.  It  seems  probable  that  the 
revival  of  adult  Rotifers  after  desiccation  is  not  so  common 
as  has  sometimes  been  supposed. 

An  almost  whimsical  instance  of  vital  resistance  is 
vouched  for  by  G-.  Tornier.  He  found  two  eggs  of  the 
common  lizard,  Lacerta  agilis,  through  which  the  rhizome 
of  a  sedge  had  grown,  dissolving  away  the  shell  at  the 
entrance  and  exit.  Each  of  the  eggs  contained  a  normal 
embryo  !  In  the  uppermost  of  the  two  eggs,  which  was 
perforated  centrally  by  the  rhizome,  there  were  actually 
three  rootlets  penetrating  the  embryonic  membranes  and 
entering  the  yolk-sac.  In  one  case  a  delicate  rootlet  had 
passed  into  the  embryo's  mouth.  Yet  the  embryos  were 
normal,  illustrating  quaintly  but  strikingly  what  we  may 
call  developmental  resistance. 

An  eel  about  a  foot  long  has  been  known  to  live  for  seventy- 
two  hours  without  water,  and  a  day's  drought  can  be 
readily  withstood.  This  tenacity  of  life  makes  it  easier 
to  admit  the  possibility  of  the  overland  journeys  which 
eels  are  alleged  to  take  when  occasion  requires. 


THE   INSURGENCE  OF  LIFE  153 

Some  interesting  illustrations  of  tenacity  of  life  have  been 
afforded  by  recent  experiments  on  the  surviving- power  of 
tissues  cut  off  from  the  living  body.  In  suitable  culture- 
media  they  can  be  kept  alive  for  many  days  and  may  even 
grow.  At  a  variable  point,  differing  for  different  tissues 
and  media,  growth  becomes  slow  and  stops  and  the  living 
fragment  dies.  In  this  connexion  Alexis  Carrel  has  de- 
monstrated a  very  instructive  fact,  showing  that  the 
death  may  be  due  to  an  accumulation  of  waste  products 
and  is  not  inevitable.  If  the  dying  fragment  is  lifted  on  a 
cataract- knife  and  bathed  and  fed,  and  bathed  and  fed 
again,  it  may  get  a  new  lease  of  life.  It  rejuvenesces. 
After  nine  washings  a  fragment  of  connective  tissue  grew 
with  great  activity  on  the  thirty-fourth  day  after  its 
excision  from  the  organism.  Thus,  within  limits,  senescence 
and  death  are  contingent,  not  necessary  phenomena. 

The  automatism  of  part  of  a  body  is  often  gruesome.  A 
turtle's  heart  will  live  for  many  days  after  its  quondam 
possessor  has  been  made  into  soup.  A  fractional  part  of  a 
silk  moth  was  observed  by  Professor  V.  L.  Kellogg  to  '  live  ' 
for  more  than  a  day,  responding  to  stimulus,  and  actually 
extruding  the  ovipositor  and  laying  a  few  eggs.  The 
separated  anterior  half  of  a  wasp  will  go  on  sucking 
syrup,  and  the  posterior  half  will  sting.  We  are  impressed 
on  the  one  hand  by  the  delicacy,  on  the  other  hand  by 
the  toughness  of  life. 

The  'Big  Trees '.—In  the  'Big  Tree'  (Sequoia 
gigantea)  of  the  western  slopes  of  the  Sierra  Nevada 
range  and  in  the  '  Redwood '  (Sequoia  sempervirens) 
of  the  Coast  Ranges,  we  have  the  impressive  surviving 
representatives  of  an  ancient  genus  (dating  from  the 
Cretaceous)  that  once  spread  over  the  Northern 


154  THE  WONDER  OF  LIFE 

Hemisphere,  but  was  brought  near  to  extinction  by  the 
severe  conditions  of  the  Great  Ice  Age.  In  size,  majesty, 
vigour,  recuperative  power,  age  and  antiquity  these 
'  Big  Trees '  command  our  admiration.  They  have  the 
distinction  of  having  had  a  longer  life  than  any  other 
living  creatures — they  make  centenarians  and  the  like 
appear  youngsters. 

The  late  Prof.  W.  R.  Dudley  recorded  some  precise  data 
on  a  subject  which  tempts  to  exaggeration.  *  Of  the  vari- 
ous trunks  of  Sequoia  gigantea  examined  ranging  from  900 
years  upward,  the  oldest  possessed  2,425  rings,  or  had  begun 
its  existence  525  years  before  the  Christian  era '.  A  tree 
near  a  perennial  stream  was  over  80  feet  in  circumference, 
ten  feet  from  the  ground,  but  was  only  1,510  years  old ; 
another  growing  on  a  hillside  not  near  a  stream,  had  suffered 
from  fire  and  from  privations  (fifty  rings  of  scarce  years 
not  covering  an  inch),  and  it  was  only  39  feet  in  circum- 
ference, ten  feet  from  the  ground,  but  it  had  attained  the 
age  of  2,171  years  and  a  height  approaching  300  feet. 

Professor  Dudley  showed  the  extraordinary  vitality  of  the 
Big  Tree  by  tracing  out  the  way  in  which  many  of  them  had 
been  able  to  '  heal '  or  cover  over  great  wounds  made  by 
fire.  What  a  tree  does  is  not  to  revitalize  what  has  been 
killed — that  is  impossible — but  to  extend  or  fold  its  living 
tissue  over  the  wound.  '  There  is  no  organic  union 
between  the  new  wood  of  the  folds  and  the  wood  of  the 
charred  surface  underneath  them,  no  healing  at  this  point 
of  contact,  in  the  ordinary  sense  of  the  word;  but 
there  is  effectual  covering,  or  healing  in  the  rarer  sense, 
according  to  the  tree  trunk's  way.'  The  process  may  take 
scores  of  years. 

The  tree  already  referred  to  which  began  its  existence  in 


THE   INSURGENCE  OF  LIFE  155 

271  B.C.  was  about  twelve  feet  in  circumference  just  above 
the  base  at  the  beginning  of  the  Christian  era.  When  it 
was  516  years  old  (A.D.  245)  it  suffered  a  burn  three  feet 
wide,  and  105  years  were  occupied  in  healing  this  wound. 
When  it  was  1,712  years  old  (A.D.  1441)  it  suffered  two  bad 
burns.  One  hundred  and  thirty-nine  years  of  growth 
followed,  including  the  time  occupied  by  the  covering  of 
the  two  wounds.  When  it  was  1 ,851  years  old  (A.D.  1580)  it 
suffered  from  a  burn  two  feet  wide  which  took  56  years  to 
heal.  When  it  was  2,068  years  old  (A.D.  1797)  a  tremendous 
fire  burned  a  great  scar  18  feet  wide  with  a  height  estimated 
at  30  feet.  In  the  103  years  that  were  vouchsafed  to  it  before 
it  was  killed,  the  tree  had  reduced  the  wound  to  fourteen 
feet  in  width,  and  it  might  have  finished  it  in  A.D.  2250, 
or  thereabouts.  *  Sequoia  gigantea  stands  practically  alone, 
sublime  among  living  objects  in  its  ability  to  withstand  an 
injury  of  this  magnitude,  and  to  endure  a  sufficient  length 
of  time  for  its  complete  recovery '.  The  resistance  to 
insect,  fungus,  and  microbe  is  hardly  less  remarkable. 
'  There  is  something  in  the  sap  of  the  Big  Tree  that  is  an 
elixir  of  life,  something  deposited  in  the  lignified  cells 
of  the  normally  formed  layers  of  wood  that  resists  in  an 
unexampled  way  the  dreadful  '  tooth  of  time  '. 

One  does  not  envy  the  man  who  can  look  at  even  a  sec- 
tion of  great  Sequoia  without  a  thrill  at  the  sight.  *  We 
have,  deep  in  their  annual  rings,  records  which  extend  far 
beyond  the  beginnings  of  Anglo-Saxon  peoples,  beyond 
even  the  earliest  struggles  for  liberty  and  democracy 
among  the  Greeks',  .  .  .  '  records  of  forest  conflagrations,  of 
the  vicissitudes  of  seasons,  of  periods  of  drought  and  periods 
of  abundant  and  favouring  rains  '.  It  is  to  be  hoped  that 
everything  feasible  will  be  done  to  protect  these  triumphs 


156  THE  WONDER  OF  LIFE 

of  life — these  sublime  instances  of  its  power  and  endurance 
— which  are  certainly  among  the  most  remarkable  products 
of  the  globe. 

The  recuperative  power  of  races  varies  within  wide  limits, 
and  it  is  often  difficult  to  suggest  why  one  type  should  have 
so  little  and  another  so  much  of  it.  The  story  of  the  tile- 
fish  (Lophobatilus  chamceleonticeps)  is  interesting  in  this  con- 
nexion. It  used  to  frequent  the  north-east  coast  of  North 
America,  in  water  about  50°  Fahr.,  and  was  much  fished 
between  1879  and  1882.  In  1882,  however,  there  was 
a  very  hard  winter,  culminating  in  a  great  storm  which  in 
one  night  almost  put  a  full  stop  to  the  tile-fish.  Over  a 
sea-area  of  some  5,000  square  miles  the  dead  fishes  were 
found  on  the  surface  in  thousands — suddenly  killed  ofE 
by  a  fall  of  temperature  below  the  limit  of  viability.  No 
tile-fish  was  seen  for  ten  years.  But  in  1902  the  small 
remnant  that  must  have  escaped  began  to  manifest  itself, 
and  the  recuperation  gradually  set  in. 


PLASTICITY 

Change  of  Habits. — The  well-known  robber-crab 
(Birgus  latro)  is  a  good  instance  of  adaptability  to  a  thor- 
oughgoing change  of  habit.  Birgus  should  be  a  seashore 
animal,  and  it  has  to  return  to  the  shore  to  spawn,  illus- 
trating the  rule  that  the  young  have  to  be  cradled  in  the 
ancestral  headquarters,  but  it  has  become  a  terrestrial 
animal.  It  goes  high  up  the  mountains,  and  Dr.  Andrews 
has  photographed  it  climbing  trees.  It  simply  walks  up, 
clinging  by  the  sharp  points  of  the  walking-legs,  hardly 
using  the  large  claws  at  all.  Of  the  robber-crabs  at  Christ- 
mas Island,  Dr.  Andrews  writes  that  they  are  easily  fright- 


THE   INSURGENCE  OF  LIFE  157 


FIG.  37. — Cross  section  through  a  land-crab  (Birgus  latro).  (After 
Semper. )  1 .  The  over-lap  of  the  cephalothorax  shield.  2.  The  respir- 
atory tufts.  3.  Two  small  gills.  4.  The  base  of  a  leg.  5.  The  ventral 
nerve-cord.  6.  The  food-canal.  7.  The  pericardium  around  the 
heart. 


ened  and  scuttle  off  backwards,  propelling  themselves  with 
their  long  anterior  legs  in  a  series  of  ungainly  jerks.  They 
seem  quite  conscious  of  the  comparative  defencelessness 
of  the  abdomen,  which  they  endeavour  to  thrust  under 
logs  or  into  holes  among  the  roots  of  trees.  But  they 
never  carry  any  protective  covering.  Their  dietary  must 
also  have  changed  greatly,  for  they  eat  fruits  of  various 
kinds  (such  as  sago-palm  and  screw-pine)  and  carrion  of 
all  sorts.  As  their  name  suggests,  they  are  incorrigible 
thieves,  stealing  from  the  camp  not  only  what  is  or 
even  looks  edible,  but  apparently  anything  that  has  been 
handled,  cooking  utensils,  bottles,  and  clothes.  Dr. 
Andrews  complains  that  he  had  a  geological  hammer 
practically  ruined  by  having  its  handle  splintered  in  the 
powerful  claws  of  one  of  the  robbers  ! 

The  case  of  the  land-crab  suggests  another  good  instance 
of  adaptation  to  change  of  habit.  It  is  to  be  found  in  a 
Philippine  crustacean,  Thalassina  anomala,  which  is  in 
some  respects  like  a  link  between  the  long-tailed  prawn 
type  and  the  hermit-crab  type.  It  is  a  common  burrower 


158  THE  WONDER  OF  LIFE 

by  the  shore  of  the  estuaries  and  makes  holes  not  only  in  the 
softer  ground,  but  in  the  hard  clay  of  the  grassy  meadows. 
In  the  latter  the  holes  go  down  till  they  are  below  the 
water-level.  The  animal  seems  able  to  live  in  poorly 
aerated  water,  as  Bate  surmised  long  ago  from  his  study  of 
preserved  specimens.  Its  habits  have  been  recently  studied 
by  Mr.  A.  S.  Pearse,  who  points  out  that  the  ability  to 
breathe  in  poorly  aerated  water  would  be  a  distinct  advan- 
tage, and  seems  to  have  been  secured  by  a  simple  contri- 
vance. The  gill-covers  or  side-flaps  of  the  shield  that  covers 
the  front  of  the  body  are  movable  on  the  dorsal  portion 
of  the  carapace  by  a  sort  of  flexible  hinge  joint.  '  An 
individual  placed  in  a  dish  will  often  move  the  sides  of  the 
carapace  in  such  a  manner  that  it  resembles  a  Vertebrate 
gasping  for  breath '.  Such  bellows-like  movements  must 
serve  to  hasten  the  current  of  water  that  is  drawn  in  over  the 
gills  and  thus  facilitate  respiration. 

As  a  good  instance  of  the  possession  of  a  new  home  we 
may  refer  to  the  freshwater  sting-rays  of  the  Ganges.  No 
fishes  are  more  characteristically  marine  than  rays  and 
skates,  yet  it  is  certain  that  there  are  several  members  of 
this  (Batoid)  family  in  the  Ganges.  Two  species,  Trygon 
fluviatilis  and  Hypolothus  sephen,  have  established  them- 
selves far  up  the  great  river.  Even  one  thousand  miles 
above  tidal  influence,  they  thrive  and  breed  freely. 

While  some  creatures  are  sensitive  specialists  as 
regards  environment,  others  are  tough  cosmopolitans. 
In  illustration  of  the  latter  we  may  refer  to  Dr.  Alcock's 
account  of  the  freshwater  crabs  (Potamonidse)  of 
India.  They  are  typically  freshwater  animals,  but  some 
can  live  both  in  brackish  water  and  in  damp  jungle.  '  They 
are  found  in  ponds,  lakes,  streams,  rivers,  and  marshes  ; 


THE   INSURGENCE  OF  LIFE  159 

and  though  they  flourish  most  at  low  or  inconsiderable 
levels  in  the  tropics  they  extend  into  the  warmer  temperate 
regions,  and  are  also  quite  common  at  considerable  eleva- 
tions in  the  torrid  zone.'  As  a  particular  example,  he 
takes  Paratelphusa  spinigera,  which  is  very  common  in  the 
swamps  of  Lower  Bengal. 

'  In  the  rainy  season  it  can  be  seen  in  any  Calcutta  tank, 
often  reposing  on  the  bank,  half  immersed  in  the  water  : 
in  the  cold  season  it  may  be  found  in  the  j heels  in  swarms, 
half-buried  in  the  mud  :  in  the  hot  season,  where  the  sur- 
face waters  dry  up,  it  digs  deep  burrows  to  get  down  to  the 
ground  water.  The  same  species,  P.  spinigera,  on  the  one 
hand,  ascends  the  Ganges  and  Jumna  as  far  as  Hardwar 
and  Saharanpur,  and  the  Jhelum  valley  to  an  elevation  of 
two  thousand  feet,  and,  on  the  other  hand,  does  not  object 
to  the  brackish  water  of  the  Gangetic  delta.' 

THE  BIOLOGY  OF  THE  SEASONS 

We  have  given  some  examples  of  what  might  be  called 
the  conquest  of  space — the  exploitation  of  the  earth,  the 
making  the  best  of  difficult  conditions,  the  circumventing 
of  obstacles ;  but  there  are  other  instances  of  the  same 
quality  of  life  which  might  be  grouped  under  the  title 
the  conquest  of  time — the  victory  over  temporal  vicissitudes. 
This  is  in  great  part  the  theme  of  a  previous  study J  and 
we  shall  confine  ourselves  here  to  a  few  illustrations. 

The  general  problem  is  how  living  creatures  suit  them- 
selves to  the  external  periodicities  of  the  seasons,  or  of 
day  and  night,  or  of  oscillations  of  climate.  In  diverse 
ways  the  internal  rhythms  of  life  have  come  to  be  adjusted 
to  the  external  periodicities.  It  is  said  that  the  tropical 
1  The  Biology  of  the  Seasons,  1911. 


160  THE  WONDER  OF  LIFE 

African  mudfish  (Protopterus)  taken  to  North  Europe, 
and  kept  with  abundant  water,  tends  to  become  dormant 
at  what  corresponds  to  the  African  dry  season,  when  it 
normally  goes  to  sleep  for  half  the  year.  It  is  said 
(precise  facts  would  be  very  valuable)  that  migrant  birds 
in  cages  become  restless  in  autumn — at  the  proper  time 
for  southward  flight — although  they  are  living  in  conditions 
of  apparent  comfort.  It  is  certain  that  many  birds  begin 
their  autumnal  migration  with  notable  punctuality  at  a 
'time  when  the  external  changes  have  not  yet  begun  to 
be  in  any  sense  compelling. 

The  point  may  be  further  illustrated  by  reference  to 
Professor  Semon's  suggestive  experiments  with  young 
Acacias  (Albizzia  lophantha).  They  had  never  been 
exposed  to  the  normal  alternation  of  day  and  night,  to 
which  acacias  are  wont  to  respond  by  expanding  or  closing 
the  leaves.  Semon  exposed  them  to  artificial  days  and 
nights  of  six  hours'  or  twenty-four  hours'  duration,  but  the 
young  plants  exhibited  the  twelve-hours'  cycle  quite 
unmistakably — though  just  a  little  altered.  After  this 
experiment,  Semon  exposed  his  plants  to  continuous  dark- 
ness or  to  continuous  illumination,  and  he  had  the  satis- 
faction of  seeing  the  twelve-hours'  cycle  still  manifesting 
itself  for  a  little.  It  gradually  became  indistinct,  as  the 
plants  gave  up  asserting  themselves  against  '  times  out 
of  joint '.  At  first,  however,  the  experiments  showed  very 
beautifully  how  the  ingrained  hereditary  periodicity  may 
struggle  against  inappropriate  external  conditions. 

It  is  interesting  to  consider  the  diversity  of  ways  in 
which  animals  meet  the  difficulties  involved  in  the  winter- 
conditions  in  North  Temperate  countries.  Many  birds, 
'  intelligent  of  the  seasons ',  as  Milton  has  it,  escape  the 


FlG.  38. — Protopterus.  A.  Capsule  cut  into,  showing  the  coiled-up  fish  with  its 
nostril  at  foot  of  the  pipe  (P).  B.  Capsule  intact,  showing  lid  (L).  (/4/fcrW. 
N.  Parker.) 


THE  INSURGENCE  OF  LIFE  161 

spell  by  flight, — a  solution  which  we  shall  presently  discuss 
in  detail.  Other  creatures,  unequal  to  the  long  and  adven- 
turous journeys  of  the  birds,  retire  into  winter-quarters, 
in  which  they  he  low,  awaiting  happier  days.  Thus  the 
earthworms  burrow  more  deeply  than  ever  below  the  reach 
of  the  frost ;  the  lemmings  tunnel  their  winding  ways  be- 
neath the  icy  crust  of  the  Tundra  ;  all  manner  of  insects 
in  their  pupa-stages  lie  inert  within  cocoons  or  other  pro- 
tective envelopes  in  sheltered  corners ;  the  frogs  bury 
themselves  deeply  in  the  mud  of  the  pond,  and  lie  there 
mouth  shut,  nose  shut,  eyes  shut,  with  the  heart  beating 
feebly,  and  breathing  through  their  skin ;  and  the  slow- 
worms  coil  themselves  up  together  in  the  penetralia  of  their 
retreats — all  trying  to  get  below  the  deadly  grip  of  the 
frost's  fingers,  and  usually  succeeding.  Let  us  take,  as  a 
diagrammatic  detail,  Professor  Arnold  Lang's  observa- 
tion, that  the  heart  of  the  snail  beats  more  and  more  slowly 
as  the  temperature  falls  and  the  animal  sinks  more  deeply 
into  hibernation.  A  heart  that  can  beat  fifty  times  a 
minute  in  summer  may  only  beat  2-36  times  a  minute  at 
a  temperature  of  2-65°C.  in  February. 

Very  effective,  too,  is  the  deep  hibernation  of  such  mam- 
mals as  hedgehog,  hamster,  and  marmot.  The  normal 
power  of  '  warmbloodedness ',  that  is,  of  keeping  an 
approximately  constant  body-temperature,  is  in  abeyance 
for  a  time ;  the  body  cools  to  a  degree  which  in  ordinary 
life  would  be  fatal ;  the  fat  accumulated  in  days  of  plenty 
is  slowly  burnt  away ;  irritability  wanes  to  a  minimum 
and  the  ordinary  reflexes  are  faint ;  the  heart  beats  feebly ; 
the  breathing  movements  may  be  scarcely  perceptible ; 
the  creature  steadily  loses  weight.  But  it  keeps  alive ! 

Others,  again,  such  as  the  Arctic  fox,  the  mountain  hare, 

M 


i6s  THE  WONDER  OF  LIFE 

the  ermine,  the  Hudson's  Bay  lemming,  and  the  ptarmigan, 
face  the  dread  enchantment  of  Winter,  but  turn  paler 
and  paler  under  the  spell,  until  they  are  as  white  as  the 
snow  itself — a  safety-giving  pallor.  They  have  a  consti- 
tutional tendency  to  change  their  colour,  and  the  external 
cold  pulls  the  trigger  that  sets  the  process  at  work.  The 
white  suit  is  of  service  for  concealment  or  in  the  chase, 
and  it  is  also  physiologically  the  most  economical  and 
comfortable  dress  for  a  warm-blooded  animal  when  the 
external  temperature  is  very  low. 

An  interesting  and  unusual  adaptation  to  the  severity 
of  winter  is  exhibited  by  the  Canadian  Ruffed  Grouse 
(Bonasa  umbellatus),  which  often  takes  refuge  among  the 
dry  soft  snow  of  drifts,  having  discovered  its  value  as  a 
non-conductor.  It  sometimes  tunnels  in,  but  it  usually 
gets  a  start  by  diving  from  a  branch  or  off  the  wing.  It 
makes  a  passage  about  two  feet  long  with  an  enlargement 
at  the  end,  and  may  lie  there  for  several  days.  Mr.  Charles 
MacNamara  observes  that  '  except  for  the  one  mark  where 
the  tunnel  begins,  the  surface  of  the  snow  is  quite  undis- 
turbed, and  no  one  would  ever  suspect  that  a  live  warm 
bird  was  concealed  in  the  drift '. 

MIGRATION  AS  AN  INSTANCE  x 

From  ancient  days  the  migration  of  birds  has  excited 
the  wonder  of  all  thoughtful  observers.  The  author  of 
the  Book  of  Job  took  note  of  the  hawk  that  stretcheth 
her  wings  towards  the  south  ;  the  Hebrew  prophet  in  his 
message  to  Israel  recalled  the  fact  that  '  the  stork  in  the 

1  In  taking  this  instance  we  have  almost  inevitably  repeated  part  of 
the  discussion  of  Migration  to  be  found  in  several  chapters  of  The 
Biology  of  the  Seasons, 


THE  INSURGENCE  OF  LIFE  163 

heavens  knoweth  her  appointed  time,  and  the  turtle  and 
the  crane  and  the  swallow  observe  the  time  of  their  coming  ' ; 
and  Homer  made  telling  use  of  the  familiar  picture  of  the 
migrating  cranes.  We  know  much  more  about  migration 
than  did  these  early  observers,  but  it  can  hardly  be  said 
that  the  wonder  is  less. 

Sometimes  the  migratory  movement  is  seen  with  almost 
startling  vividness,  so  that  even  the  careless  are  impressed  ; 
at  other  times  the  annual  tide  flows  and  ebbs  without 
calling  for  much  remark.  On  an  island  like  Heligoland, 
which  lies  on  a  favourite  migratory  route  and  is  without 
any  resident  birds  of  its  own  (save  sparrows),  it  is  very 
impressive  to  see  wave  after  wave  of  migrants  strike  the 
rocky  shore  in  the  autumnal  westward  and  south-westward 
movement.  The  birds  used  to  light  in  thousands  on  the 
small  fields  now  given  over  to  batteries,  and  rest  for  a 
few  hours  before  continuing  their  journey.  Observers 
on  the  Isles  of  Scilly  sometimes  see  hundreds  of  thousands 
of  birds  of  the  same  kind  flying  from  the  English  coast ; 
and  taking  many  hours  to  pass.  And  many  who  have 
travelled  on  a  steam-ship  up  the  West  Coast  of  Africa  in 
autumn  have  had  the  good  fortune  to  see  enormous  numbers 
of  birds  making  their  way  south,  looking  from  a  distance 
like  dense  clouds  of  smoke  swirling  rapidly  close  to  the 
water.  Some  of  the  migrants  often  rest  on  the  ship  for 
a  while,  until  they  feel  that  they  are  being  carried  the 
wrong  way.  Then  they  rise  into  the  air  and  make  for  the 
south  again. 

Not  less  interesting  is  it  to  watch  the  actual  arrival  of 
the  summer  visitors,  especially  when  they  come  in  after  a 
long  sea- voyage,  and  sink  to  the  ground  as  if  welcoming 
a  rest.  When  one  sees  swallows  and  the  like  arriving  on 


164  THE  WONDER  OF  LIFE 

the  coast  of  Cornwall,  for  instance,  one  recalls  Tennyson's 
picture — 

Faint  as  a  climate-changing  bird  that  flies 
All  night  across  the  darkness,  and  at  dawn 
Falls  on  the  threshold  of  her  native  land, 
And  can  no  more. 

But  whether  the  migration  be  seen  in  a  striking  or  in  an 
inconspicuous  form,  it  can  never  fail  to  produce  the  thrill 
of  wonder  in  the  reflective  observer. 

Lines  of  Inquiry. — It  may  be  said  broadly  that  there 
are  three  main  lines  of  inquiry,  each  reasonable  and  promise- 
ful.  Each  has  indeed  already  led  to  important  results. 
First,  there  is  the  method  of  registering  the  arrivals  and 
departures,  the  changes  and  movements,  in  a  small  area 
like  Heligoland  or  Fair  Island,  which  can  be  thoroughly 
explored.  We  cannot  mention  these  two  islands  without 
thinking  at  once  of  Gatke  and  Eagle  Clarke.  Second, 
there  is  the  method  of  collecting  data,  year  after  year,  from 
observers  scattered  over  a  wide  area,  both  inland  and  on 
lighthouses  and  lightships,  who  record  times  of  arrival 
and  departure,  great  wave-like  incursions,  marked  increase 
and  decrease  in  numbers,  and  the  like.  This  is  the  method, 
painstaking  and  laborious,  and  sure  to  yield  generalizations 
in  the  long  run,  which  has  been  followed  for  eight  years 
now  (1914)  by  the  British  Ornithologists'  Club.  Third, 
there  is  the  method,  which  we  may  particularly  associate 
with  the  name  of  Dr.  Thienemann  of  Rossitten,  of  marking 
large  numbers  of  migrants  with  indexed  aluminium  rings, 
in  the  hope  of  hearing  again  of  the  whereabouts  of  a  small 
percentage  in  their  winter-quarters  or  summer- quarters 
or  en  route  between  the  two.  This  method  has  already  led 
to  the  mapping  out  of  a  more  than  provisional  migrational 


THE  INSURGENCE  OF  LIFE  165 

route  for  the  White  Stork  in  its  southward  or  south-east- 
ward autumnal  flight. 

Some  Fundamental  Facts. — Migration  is  not  to  be 
confused  with  the  invasion  of  a  new  territory  in  search  of 
food  and  under  pressure  of  increasing  population — though 
it  may  have  originated  in  some  cases  in  this  way.  It  is  a 
regularly  recurrent  seasonal  movement, — an  oscillation 
between  summer- quarters  and  winter- quarters,  between 
a  breeding  and  nesting  place  and  a  feeding  and 
resting  place.  And  one  of  the  fundamental  facts  is  that 
birds  always  nest  in  the  colder  area  of  their  migratory  range. 

For  the  Northern  Hemisphere  it  must  be  admitted  that 
bird- migration  is  a  general  phenomenon,  though  it  differs 
greatly  in  its  range  and  conspicuousness.  In  many  parts 
of  Scotland  the  curlews  pass  at  the  beginning  of  winter 
from  the  exposed  moorland  to  the  neighbourhood  of  the 
sea-shore,  where  it  is  easier  to  procure  food ;  and  flocks 
of  sixty  or  more  of  these  shy  birds  are  often  seen  at  work 
among  the  jetsam.  This  is  migration  within  a  short  radius. 
It  may  be  contrasted  with  that  of  the  Arctic  tern  which 
the  Scotia  explorers  found  '  wintering '  in  the  Antarctic 
summer  in  74°  S.  lat. — '  the  greatest  latitudinal  range  of 
any  vertebrate  animal '. 

It  is  said  that  many  of  the  godwits  which  nest  in  eastern 
Siberia  winter  in  New  Zealand,  but  the  '  ringing  method  ' 
should  be  used  to  test  these  generalizations.  It  is  certain, 
of  course,  that  many  godwits  leave  the  north  of  New 
Zealand  in  spring,  that  many  godwits  nest  in  Eastern  Siberia, 
and  that  many  godwits  return  to  New  Zealand  in  October. 
It  is  necessary,  however,  to  prove  that  the  birds  that  spent 
some  summer  months  in  Siberia  were  the  birds  that  enjoyed 
in  the  same  year  a  second  summer  in  New  Zealand. 


166  THE  WONDER  OF  LIFE 

Referring  to  the  general  occurrence  of  migration,  Professor 
Newton  said — 

'  I  cannot  point  out  any  species  which  I  believe  to  be,  as  a 
species,  entirely  non-migratory.  No  doubt  many  persons 
would  at  first  be  inclined  to  name  half  a  dozen  or  more  which 
are  unquestionably  resident  with  us  during  the  whole  year, 
and  even  inhabit  the  same  very  limited  spot.  But  I  think 
that  more  careful  observation  of  the  birds  which  are  about 
us,  to  say  nothing  of  an  examination  of  the  writings  of 
foreign  observers,  will  show  that  none  of  them  are  entirely 
free  from  the  migratory  impulse.' 

He  instanced  the  Hedge  Sparrow  which  seems  so  station- 
ary on  Britain,  and  yet  is  well  known  as  a  migrant  on  the 
Continent. 

Our  knowledge  of  bird- movements  in  the  Southern 
Hemisphere  is  very  scanty,  and  must  be  left  out  of  account 
at  present ;  but  for  the  Northern  Hemisphere  it  is  a  very 
familiar  fact  that  the  birds  of  any  country  can  be  classified, 
from  the  migration  point  of  view,  into  five  sets  : — 

(1)  There   are    the  summer- visitors,  such   as  swallow, 
swift,  cuckoo,  nightingale,  and  so  on  through  the  long  list 
(mostly  insectivorous,  one  should  note),  who  arrive  from 
the    South  in  Spring,  nest  and  breed  within  our  bounds, 
and  return  in  late  summer  or  autumn  '  to  warmer  lands 
and  coasts  that  keep  the  sun '. 

(2)  Against  these  we  have  to  place  the  winter- visitors, 
such  as  fieldfare  and  redwing,  both  first  cousins  of  the 
thrush,  the  snow  bunting,  and  many  of  the  northern  ducks 
and  divers,  who  nest  in  the  far  North,  but  come  South  in 
winter. 

(3)  In  a  set  by  themselves  we  may  rank  the  birds- 
of-passage   in  the  stricter  sense,  like  some  of  the  sand- 


THE   INSURGENCE  OF  LIFE  167 

pipers,  the  great  snipe,  and  the  little  stint.  They  rest 
for  a  short  time  only  in  a  country  like  Britain,  on  their 
way  further  south  or  further  north. 

(4)  Then  there  are  the   '  partial  migrants ',   who  are 
always  represented  in  the  country  or  area  in  question, 
but  not  always  by  the  same  individuals.     That  is  to  say, 
some  individuals  leave  the  country  and  others  do  not ; 
and  the  place  of  those  who  go  is  often  taken  by  other 
individuals  from  elsewhere.     Thus  in  many  parts  of  Scot- 
land  one    may   see    lapwings   every  month  of  the   year, 
and  yet  there  is  a  regular  autumnal  migration  of  lapwings 
from  Scotland  to  Ireland.     There  are   always   goldfinches 
to  be  found  in  the  South  of  England,  but  there  is  a  regular 
migration   southwards   in   October  and   a   corresponding 
return  in  April.     Recent  research  has  shown  that  the  list 
of  '  partial  migrants '  is  a  long  one, — longer  than  used  to 
be  thought. 

(5)  There  remain  the  strictly  resident  birds — such  as, 
in  Britain,  the  red  grouse  and  the  house  sparrow  (to  take 
a  sacred  and  a  profane  example).     The  rook  and  the  robin 
may  serve  as  two  other  instances.     But  the  list  has  been 
greatly  reduced  by  the  discovery  that  many  of  the  reputed 
residents  are  really  partial  migrants.     It  is  obvious  that 
no  hard  and  fast  line  can  be  drawn ;   and  it  goes  without 
saying  that  species  which  are  resident   in  one    country 
may  be  migratory  in  another,  just  as  the  summer-visitors 
of  one  country  are  of  course  the  winter- visitors  of  another. 

Perhaps  another  division  should  be  made  for  the  inter- 
esting '  casual  vagrants  '  who  occasionally  turn  up  in  a 
country,  far  of!  their  normal  line  of  movement.  The 
American  Kildeer  Plover  shot  in  Aberdeenshire  in  1867 
is  a  good  instance. 


i68  THE  WONDER  OF  LIFE 

The  migration  of  birds  is  a  seasonal  phenomenon,  and 
it  seems  legitimate  to  rank  among  the  fundamental  facts 
the  contrast  that  obtains  between  the  autumnal  and  the 
vernal  movements.  There  is  some  uncertainty  in  regard 
to  various  features  of  the  contrast,  but  that  it  is  marked 
must  be  admitted.  The  autumnal  migration,  on  the 
whole  southwards,  is  less  intense  than  the  return  migration 
in  spring.  One  often  observes  a  good  deal  of  preliminary 
fuss  and  not  a  little  dallying  before  the  autumnal  migrants 
get  fairly  under  way.  They  make  trial  journeys  and  may 
begin  their  pilgrimage  with  short  stages.  The  young 
birds  are  said  to  get  restless  first ;  the  old  males  are  said  to 
linger  longest.  It  may  be  that  the  adults  are  kept  back 
by  the  need  of  recuperation  after  their  family  cares,  and 
also  by  a  moult  after  which  the  feathers  damaged  by  the 
summer's  wear  and  tear  are  replaced.  Every  one  knows 
the  exceptional  case  of  the  cuckoo,  whose  offspring,  carefully 
fostered  by  other  birds,  do  not  leave  Britain  for  six  weeks 
or  so  after  all  their  real  parents  have  gone. 

In  spring,  on  the  other  hand,  the  movement  is  much 
more  intense,  impetuous,  and  urgent.  The  adult  males 
seem  usually  to  take  the  lead,  '  love-prompted '  ;  then 
follow  the  adult  females ;  the  immature  birds,  who  will 
not  breed  for  a  season  or  two,  bring  up  the  rear.  Thus 
the  vernal  order  is  the  reverse  of  the  autumnal  order. 
There  is  some  evidence,  also,  that  the  spring  journey  is 
more  direct  than  the  autumn  journey.  Shortcuts  are  found 
and  impelling  haste  is  the  characteristic  feature.  Where 
the  sexes  fly  separately,  it  may  be  that  this  is  because  they 
naturally  fly  at  different  rates. 

As  a  striking  illustration  of  the  contrast  between  the 
vernal  and  the  autumnal  migration  movement,  we  may 


THE  INSURGENCE  OF  LIFE  169 

recall  Audubon's  observation  in  reference  to  the  Rice 
Bird,  Dolichonyx  oryzivora,  that  it  flies  in  Spring  by  night, 
and  in  Autumn  by  day. 

Another  general  fact  that  impresses  us  in  regard  to 
migration  is  its  regularity  and  success.  When  weather 
conditions  are  very  unpropitious,  there  is  often  great 
mortality.  The  streets  of  towns  are  sometimes  strewn 
with  the  corpses  of  thousands  of  birds  that  have  gone 
astray  and  succumbed  to  the  cold.  As  many  as  five 
hundred  nightingales  have  been  gathered  in  a  single  day 
from  one  small  town.  Large  numbers  of  migrants  perish 
every  year  by  dashing  themselves  against  the  windows  of 
lighthouses.  But,  on  the  whole,  the  striking  fact  is  not 
the  number  of  failures  but  the  large  proportion  of  successes. 
This  is  the  more  striking  when  the  difficulties  of  a  long 
migration- journey  are  borne  in  mind.  What  we  are  made 
to  feel  is  that  migrating  is  an  old-established  business ; 
it  has  been  going  for  so  many  hundreds  of  thousands  of 
years  that  it  has  acquired  a  certain  smoothness.  A  thrush 
born  in  the  North  of  Scotland  was  found  at  the  end  of  its 
first  summer  near  Lisbon — a  long  journey  for  an  inex- 
perienced traveller  who  is  hardly  counted  as  a  migrant 
at  all.  And  there  are  many  similar  instances. 

The  feature  of  regularity  is  also  illustrated  by  the  re- 
markable punctuality  of  arrival  and  departure  which  is 
usually  exhibited,  except,  indeed,  when  the  meteorological 
conditions  are  unusual.  Fog  and  head-winds  may  delay 
arrival ;  a  summer  that  has  favoured  the  increase  of  insect 
life  may  induce  birds  to  postpone  their  departure ;  but, 
on  the  whole,  there  is  a  remarkable  temporal  regularity 
in  the  comings  and  goings. 

While  there  is  great  regularity  in  many  cases,  it  must 


170  THE  WONDER  OF  LIFE 

also  be  borne  in  mind  that  certain  of  our  summer  visitors 
in  Britain  keep  on  arriving  for  a  long  time — different 
contingents  probably  coming  from  different  winter-quar- 
ters. Thus  in  the  sixth  Keport  of  the  Migration  Com- 
mittee of  the  British  Ornithological  Club  it  is  recorded  that 
'  the  immigration  of  the  wheatear  (including  both  races) 
extended  over  a  longer  period  than  that  taken  by  any 
other  species,  the  first  arrivals  (in  1910)  being  observed 
on  March  6,  the  last  on  May  19.  Other  species  occupying 
a  prolonged  period  were  the  willow- warbler  (March  19 
to  May  19)  and  the  whin-chat  (March  26  to  May  23), 
while  the  shortest  time  seems  to  have  been  taken  by  the 
wood- warbler  (April  11  to  May  6).  The  average  length  of 
the  arrival  period  for  1910  was  about  five  or  six  weeks '. 
For  the  same  year  the  first  bird  to  return  was  the  chiff-chaff 
on  March  5,  but  except  for  a  few  species  the  immigration 
did  not  really  set  in  till  April  2.  Most  of  it  was  over  by 
the  end  of  the  third  week  in  May.  The  largest  movement 
occurred  on  May  2,  when  no  fewer  than  twenty-five 
different  species  arrived  simultaneously  on  the  British 
coasts. 

On  the  whole,  however,  the  regularity  of  the  migratory 
movement  is  impressive,  and  Professor  Alfred  Newton 
wrote  thus  about  it  long  ago — 

'  Foul  weather  or  fair,  heat  or  cold,  the  puffins  repair  to 
some  of  their  stations  as  regularly  on  a  given  day  as  if 
their  movements  were  timed  by  clock-work.  Whether  they 
have  come  from  far  or  from  near  we  know  not,  but  other 
birds  certainly  come  from  a  great  distance,  and  yet  they 
make  their  appearance  with  scarcely  less  exactness.  Nor 
is  the  regularity  with  which  certain  species  disappear  much 
inferior ;  every  observer  knows  how  abundant  the  swift 


THE  INSURGENCE   OF  LIFE  171 

is  up  to  the  time  of  its  leaving  its  summer  home,  and  how 
rarely  it  is  seen  after  that  time  is  past.' 

Still  more  remarkable  is  the  fact  of  spatial  regularity. 
For  in  a  few  cases  (doubtless  to  be  increased)  we  have 
conclusive  proof  of  a  bird's  return  to  its  birthplace. 
A  swallow  marked  as  a  youngster  with  an  aluminium 
ring  has  been  known  to  return  the  following  year,  not 
merely  to  the  same  county  or  parish,  but  to  the  same  farm- 
yard— a  striking  instance  of  precision  in  the  sense  of 
locality,  and  of  a  constitutional  home-sickness  bringing 
the  bird  back  from  its  winter-quarters  (probably  in  Africa) 
to  its  birthplace  in  England.  The  same  return  to  the 
original  homestead  has  been  proved  in  the  case  of  the 
house-martin  and  the  stork,  and  is  certainly  one  of  the 
most  wonderful  facts  about  migration. 

Concrete  Problems  of  Migration. — One  of  the  im- 
portant questions  which  patient  investigations,  like  those 
of  Mr.  Eagle  Clarke,  are  in  process  of  answering,  concerns 
the  routes  which  birds  follow  in  their  migratory  flight. 
On  the  basis  of  observations  made  at  lighthouses  and 
lightships  and  at  strategic  inland  stations,  it  has  been 
possible  to  map  out  certain  favourite  routes.  Equally 
useful  results  have  rewarded  '  the  ringing  method  '  pursued 
by  Dr.  Thienemann  at  Rossitten,  Dr.  Mortensen  in  Holland, 
Aberdeen  University  and  the  editor  of  British  Birds,  in 
Britain,  and  by  others  on  the  Continent  and  in  the  United 
States. 

The  localities  where  any  particular  kind  of  bird  was 
originally  ringed  and  was  subsequently  captured,  are 
registered  on  a  map  (a  different  one  for  each  kind  of  bird), 
and  as  the  records  of  rings  accumulate  in  the  course  of  years 
the  distribution  of  dots  or  crosses  on  the  map  begins  to 


172  THE  WONDER  OF  LIFE 

show  the  nature  of  the  migratory  movement  with  an 
accuracy  proportionate  to  the  number  of  data.  The  marks 
may  show  an  irregular  diffusion  over  a  wide  area,  which 
would  indicate  the  absence  of  well- defined  paths  ;  or  they 
may  show  a  definite  strand  or  curve,  which  would  indicate 
one  of  the  favourite  paths.  Thus  Dr.  Thienemann  has  been 
able  to  trace  the  migration  of  the  stork  with  considerable 
precision.  There  is  an  autumnal  movement  from  the  north 
to  the  south-east  as  far  as  South  Africa  ;  and  a  vernal  return 
to  the  natal  district,  sometimes  within  a  few  miles  of  the 
birthplace,  was  proved  in  some  cases.  The  rings  were 
returned  from  Damascus,  Alexandria,  the  Blue  Nile,  Rhode- 
sia, and  further  south.  One  of  the  birds  recorded  from 
the  Kalahari  desert,  8,600  kilometres  from  its  northern 
home,  had  been  killed  for  food  by  a  native,  who  threw  it 
away,  as  uncanny,  when  he  caught  sight  of  the  ring.  Two 
young  storks,  nine  months  old,  were  found  in  Basutoland, 
9,600  kilometres  from  home. 

In  the  same  way  it  has  been  made  clear  that  there  is 
among  hooded  crows,  for  instance,  a  great  westward  move- 
ment in  autumn,  e.g.  from  Finland  along  the  shores  of 
the  Baltic,  and  that  there  is  a  subsequent  curve  towards 
the  South.  This  westward  and  then  southward  curve 
seems  to  be  true  of  many  birds  in  North  Europe.  Certain 
contingents  seem  to  swerve  southwards  by  the  valleys 
of  the  Rhine  and  the  Rhone,  and  then  across  the  Mediter- 
ranean to  North  Africa.  Other  contingents  seem  to  go 
further  westwards,  crossing,  it  may  be,  by  way  of  Heligoland 
to  the  South  of  England,  and  thence  across  to  France, 
Spain,  and  Portugal,  finally  landing  like  the  others  in 
North  Africa.  For  some  other  birds,  like  the  swallow 
and  the  Red-Spotted  Bluethroat,  there  is  considerable 


THE  INSURGENCE  OF  LIFE  173 

evidence  of  a  more  direct  north  to  south  movement  in 
autumn.  Large  numbers  of  swallows  are  seen  in  autumn 
making  their  way  down  the  west  coast  of  Africa,  perhaps 
reaching  the  Cape  ;  those  from  Eastern  Europe  are  said 
to  work  their  way  southwards  by  the  Nile  Valley.  Cor- 
responding species  or  varieties  in  North  America  seem  to 
fly  to  Brazil,  and  in  North  Asia  to  Burmah. 

It  is  not  merely  in  regard  to  the  routes  followed  by 
migratory  birds  that  we  are  in  ignorance ;  we  are  in  most 
cases  quite  unable  to  say  where  our  summer  visitors  pass 
the  winter.  We  know  that  they  leave  us  for  the  south, 
and  we  know  that  birds  of  that  kind  become  numerous  in 
the  late  autumn  in  some  other  area — the  shores  of 
the  Mediterranean,  Arabia,  West  Africa,  South  Africa 
and  so  on,  but  what  we  wish  to  be  able  to  do  is  to  make 
a  precise  statement  to  the  effect  that  certain  summer 
visitors  of  the  Midlands  of  England  spend  their  winter  on 
the  Gold  Coast  or  elsewhere.  Perhaps  this  will  eventually 
become  possible  if  the  bird-marking  method  is  prosecuted 
for  a  long  stretch  of  years.  Another  question  of  great 
interest,  which  must  wait  for  its  answer  until  many  more 
data  accumulate,  is  whether  the  re  turn- journey  in  spring 
is  by  a  route  different  from  that  of  the  autumnal  journey. 

Other  matters  for  investigation,  which  must  be  patiently 
continued  without  hurrying  towards  an  answer,  are  the 
altitude  and  the  velocity  of  the  migratory  flight,  and  its 
relation  to  weather-conditions.  While  enormous  armies  of 
larks,  starlings,  thrushes,  and  some  other  birds  have  been 
seen  flying  very  low  across  the  sea,  it  is  probable  that 
most  migrants  fly  at  a  considerable  height.  Careful 
observations  made  by  von  Lucanus  lead  to  the  conclusion 
that  it  is  very  unusual  for  birds  to  migrate  at  altitudes  above 


174  THE  WONDER  OF  LIFE 

3,000  feet.     Some    astronomers,   however,   report    seeing 
birds  at  elevations  of  10,000  feet. 

Gatke  estimated  the  speed  of  migrating  plovers,  curlews, 
and  godwits,  crossing  Heligoland,  at  nearly  four  miles  a 
minute,  and  he  calculated  the  speed  of  Hooded  Crows, 
crossing  the  North  Sea,  at  108  geographical  miles  per  hour. 
He  credited  the  little  Northern  Bluethroat  with  a 
velocity  of  180  geographical  miles  per  hour.  It  seems 
to  be  the  general  opinion  of  experts  that  these  figures 
are  far  too  high.  Dr.  J.  Thienemann's  observations  at 
Rossitten  in  1909  led  to  such  averages  as  the  following  : 
Sparrow-Hawk,  25£  miles  per  hour;  Hooded  Crow,  31  J; 
Rook,  32| ;  Chaffinch,  32|;  Linnet,  34f;  Peregrine  Falcon, 
37;  Jackdaw,  38J ;  Starling,  46£.  Some  other  careful 
observers  have  estimated  the  migratory  rate  of  many  birds 
at  about  a  hundred  miles  an  hour.  It  is  reported  that  a 
marked  swallow  flew  from  Compiegne  to  Antwerp,  about 
145  miles,  in  1  hour  8  minutes  ! 

It  is  certain  that  many  a  bird  may  attain  in  its  everyday 
life  to  a  velocity  of  fifty  miles  an  hour,  and  it  is  probable 
that  twice  as  fast  is  a  safe  estimate  for  the  rate  of  many  a 
migratory  flight,  when  the  whole  life  is  raised  to  a  higher 
pitch. 

And  as  to  meteorological  conditions  it  becomes  increas- 
ingly clear  that  birds  in  their  migrations  are  somewhat 
strikingly  indifferent  to  the  weather,  unless,indeed,  it  reaches 
a  high  degree  of  storminess  or  f ogginess  or  unpropitiousness 
generally.  It  seems  that  the  weather- conditions  which 
obtain  when  and  where  a  mass-movement  begins  are  of 
much  more  moment  than  those  into  which  the  birds  pass 
in  the  course  of  their  flight. 

Deeper  Problems  of  Migration. — It  is  interesting  to 


THE   INSURGENCE  OF  LIFE  175 

inquire  where  we  should  rank  migration  on  the  inclined 
plane  of  animal  activities,  but  no  secure  answer  can  be 
given  in  the  present  state  of  science.  It  seems  to  partake 
very  largely  of  the  nature  of  instinct,  that  is  to  say,  birds 
have  a  specific  hereditary  preparedness  or  disposition  for 
their  migratory  movements,  which  enables  them  to  go 
through  with  them  without  education  or  experience.  But 
this  does  not  exclude  the  view  that  birds  have  their  wits 
about  them  as  they  fly,  for  many  instinctive  activities 
show  a  spice  of  intelligence.  Nor  does  it  exclude  the  view 
that  birds  migrate  more  successfully  as  they  grow  older, 
for  instinctive  routine  may  be  intelligently  perfected  by 
practice.  That  the  migratory  activity  has  an  instinctive 
basis  is  suggested  by  its  regularity  and  orderliness,  without 
much  individuality  and  with  little  hint  of  caprice  ;  by  the 
preparations  made  before  there  is  any  real  need ;  more- 
over it  must  be  remembered  that  none  of  our  summer 
visitors  have  any  personal  experience  of  wintry  conditions, 
literally  knowing  no  winter  in  their  year ;  by  the  success 
with  which  many  young  birds  carry  it  through,  apparently 
unguided  and  untutored ;  by  a  few  observations  of  the 
restlessness  shown  at  the  proper  time  by  comfortably  caged 
migrants ;  and  by  the  sporadic  occurrence  of  other  true 
migrations  in  widely  separated  divisions  of  the  animal 
kingdom. 

Periodic  movements  occur  in  many  other  creatures  besides 
birds — in  landcrabs,  in  fishes  like  salmon  and  eel,  herring 
and  mackerel,  in  turtles,  in  lemmings  and  field  mice,  in 
some  deer,  in  eared  seals  and  in  most  cetaceans,  such  as 
the  bottle-nose  whale,  the  right  whale,  and  the  white- 
beaked  dolphin.  The  term  migration  should  not  be  used, 
however,  without  qualification,  unless  the  movement  is  really 


176  THE  WONDER  OF  LIFE 

periodic — a  recurrent  seasonal  movement.  Thus  we  regard 
the  turtles'  voyage  to  the  egg-laying  beach  as  migratory, 
while  the  lemmings'  march  is  not.  Similarly  the  move- 
ments of  the  salmon  and  the  eel  are  much  more  worthy  of 
being  ranked  as  migratory  than  are  those  of  the  mackerel 
and  herring. 

The  movements  of  whales  are  believed  to  depend  in  great 
part  on  the  distribution  of  the  organisms  on  which  they 
feed,  and  perhaps  in  part  on  ocean  currents.  But  accord- 
ing to  Guldberg,  there  is  also  a  reproductive  factor.  Gravid 
females  seek  calm  and  shallow  waters.  It  must  be  remem- 
bered, however,  that  distance  does  not  count  much  with 
these  powerful  swimmers,  and  just  as  a  gull  may  cross  the 
Atlantic  (Germany  to  Barbadoes)  without  the  fact  mean- 
ing very  much,  so  a  whale's  movements  may  be  much 
less  significant  than  those  of  a  salmon. 

If  it  be  granted  that  the  migratory  activity  has  an  inborn 
instinctive  basis,  we  look  none  the  less  for  the  immediate 
causes  or  stimuli  which  pull  the  trigger  twice  a  year  at  the 
proper  time.  In  the  case  of  the  autumnal  movement,  we 
think  of  the  increasing  cold  and  the  decreasing  shelter,  of 
stormy  weather  and  the  shortening  of  the  daylight  hours 
available  for  food-collecting,  and  of  the  dwindling  supply 
of  insects  and  slugs,  fruits  and  seeds,  and  so  on.  But 
we  shall  probably  go  wrong  if  we  regard  these  unpropitious 
conditions  as  more  than  liberating  stimuli,  which  act  on  a 
prepared  state  of  mind. 

The  stimuli  that  prompt  the  northward  journey  in  spring 
are  more  difficult  to  state,  especially  when  we  take  into 
account  the  great  diversity  of  the  winter- quarters  and 
the  fact  that  a  large  proportion  of  the  returning  migrants 
are  immature.  Probably  the  conditions  of  temperature, 


THE   INSURGENCE  OF  LIFE  177 

humidity,  and  food  supply  are  such  as  to  exclude,  for 
many  kinds  of  birds,  the  possibility  of  nesting  in  the  south. 
Perhaps  in  some  cases  the  bird's  constitution  is  such  that  it 
cannot  become  reproductive  without  the  subtle  stimulus 
implied  in  a  return  to  the  conditions  of  the  original  birth- 
place. Perhaps  too  there  are  lingering  memories  of  the 
abundant  and  pleasant  food — whether  berries  or  mos- 
quitoes— to  be  had  in  the  North.  Both  on  the  repro- 
ductive and  on  the  nutritive  side  there  may  be  a  sort  of 
constitutional  home-sickness. 

It  is  difficult  to  get  beyond  mere  speculation  in  regard 
to  the  origin  of  the  migratory  activity.  The  living  organ- 
ism is  not  merely  a  responsive  plastic  system  which  the 
environment  subjects  to  various  experiences ;  it  is  a  crea- 
ture that  experiments.  Migration  was  an  experiment,  an 
'  inborn  inspiration  ', — probably  to  begin  with  of  germinal 
origin — in  the  face  of  untoward  conditions.  The  new  line 
of  solution,  peculiarly  natural  to  a  flying  creature,  was  to 
evade  the  difficulties,  instead  of  facing  them.  Thus,  instead 
of  hibernating  or  laying  on  fat  or  making  a  great  store  of 
food,  birds  migrated  before  the  approach  of  winter.  It 
was  a  stroke  of  genius  to  discover  that  the  prison  doors 
were  open. 

Our  view,  then,  is  this,  that  an  original  instinctive 
mutation  must  be  postulated,  which  amounted  to  '  a  new 
idea ',  but  was  not  an  idea,  which  found  expression  in  a 
timeous  restlessness,  in  sensory  alertness,  in  adventurous 
experiment,  and  in  a  power  of  flying  more  or  less  in  one 
direction.  Perhaps  we  see  something  like  the  beginning  of 
it  to-day  in  animals  which  seem  to  be  sensitive  to  remote 
warnings  of  an  impending  storm,  and  take  refuge  accord- 
ingly. Given  a  beginning,  we  can  understand  the  diffusion, 


178  THE  WONDER  OF  LIFE 

augmentation  and  specialization  of  the  migratory  instinct 
on  ordinary  Darwinian  lines.  Discriminate  elimination 
of  the  dull,  the  sluggish,  the  wilful,  the  inexpert  would 
gradually  raise  the  standard  of  migratory  capacity  mil- 
lennium after  millennium. 

As  to  the  actual  historical  conditions  that  justified  the 
migration  experiment  and  sustained  the  discriminate 
elimination  of  the  inexpert,  there  are  two  theories,  both 
of  which  may  be  true.  On  one  theory,  our  present-day  sum- 
mer visitors  were  once  at  home  over  a  great  part  of  the 
Northern  Hemisphere  which  once  had  a  much  warmer  and 
more  equable  climate  than  it  now  enjoys.  Then  there 
was  no  need  for  much  migration,  though  most  of  the 
birds  would  probably  seek  to  get  away  from  the  warmer 
areas  at  the  breeding  and  brooding  time,  and  away  from 
the  more  exposed  northern  outposts  when  winter  came. 
But  if  the  climate  changed  and  became  steadily  more 
severe,  if  the  winters  lengthened  and  the  snowline  crept 
lower  and  lower  down  on  the  mountains,  if  great  glaciers 
spread  southwards,  and  so  on,  then  very  gradually  birds 
had  to  migrate  further  and  further  south  in  winter  and  were 
able  to  penetrate  less  and  less  far  into  the  north  in  spring. 
When  the  climate  changed  again  for  the  better,  and  the 
ice  retreated  pole-wards,  there  came  about  a  re-coloniza- 
tion of  the  North  Temperate  zone  as  a  breeding  area.  There 
was  a  return  to  the  old  racial  haunts  which  the  Ice  Ages  had 
rendered  temporarily  uninhabitable. 

In  general  terms,  then,  the  present-day  spring  migration 
northwards  implies  an  organic  reminiscence  of  the  original 
headquarters  before  the  Ice  Ages ;  and  the  present-day 
autumn  migration  southwards  implies  an  organic  remini- 
scence of  the  second  home  which  was  discovered  under  the 


THE  INSURGENCE  OF  LIFE  179 

stress  of  the  glacial  intrusion.  But  too  much  must  not 
be  made  of  the  Ice  Age,  since  we  know  that  there  is  migra- 
tion in  the  Southern  Hemisphere  as  well  as  in  the  Northern. 

The  other  theory,  for  which  there  is  perhaps  most  to  be 
said,  lays  the  emphasis  on  the  food-supply.  Many  birds 
are  prolific,  and  overcrowding  is  apt  to  occur.  Instead  of 
crowding  in  one  area  all  the  year  round,  and  involving 
themselves  in  want,  birds  learned,  like  the  Swiss  peasants, 
to  exploit  two  areas,  each  for  about  half  of  the  year.  They 
tended  to  push  further  and  further  northward  in  spring, 
exploring  and  exploiting  new  grounds,  staying  as  long  as 
they  could,  and  retreating  before  the  breath  of  winter 
to  their  old  home  in  the  south,  or,  in  many  cases,  far 
beyond  that.  It  was  probably  most  effective  to  go  as  far 
north  as  possible  before  settling  down  to  family  life.  A 
noteworthy  fact  is  that  the  more  prolific  birds  tend  to  have 
the  wider  migratory  range. 

The  importance  of  natural  selection  in  connexion  with 
migration  was  clearly  pointed  out  by  Alfred  Russel  Wallace 
in  1874  :— 

'  It  appears  to  me  probable  that  here,  as  in  so  many  other 
cases,  "  survival  of  the  fittest  "  will  be  found  to  have  had  a 
powerful  influence.  Let  us  suppose  that  in  any  species  of 
migratory  bird,  breeding  can  as  a  rule  be  only  safely  accom- 
plished in  a  given  area  ;  and  further,  that  during  a  great 
part  of  the  rest  of  the  year  sufficient  food  cannot  be  obtained 
in  that  area.  It  will  follow  that  those  birds  which  do  not 
leave  the  breeding  area  at  the  proper  season  will  suffer, 
and  ultimately  become  extinct ;  which  will  also  be  the  fate 
of  those  which  do  not  leave  the  feeding  area  at  the  proper 
time.  Now,  if  we  suppose  that  the  two  areas  were  (for 
some  remote  ancestor  of  the  existing  species)  coincident,  but 


i8o  THE  WONDER  OF  LIFE 

by  geological  and  climatic  changes  gradually  diverged  from 
each  other,  we  can  easily  understand  how  the  habit  of 
incipient  and  partial  migration  at  the  proper  seasons  would 
at  last  become  hereditary,  and  so  fixed  as  to  be  what  we 
term  an  instinct.  It  will  probably  be  found  that  every 
gradation  still  exists  in  various  parts  of  the  world,  from  a 
complete  coincidence  to  a  complete  separation  of  the  breed- 
ing and  subsistence  areas  ;  and  when  the  natural  history  of 
a  sufficient  number  of  species  in  all  parts  of  the  world  is 
thoroughly  worked  out,  we  may  find  every  link  between 
species  which  never  leave  a  restricted  area  in  which  they 
breed  and  live  the  whole  year  round,  and  those  other  cases 
in  which  the  two  areas  are  absolutely  separated '  (Nature, 
October  8, 1874,  p.  459). 

Way -Finding. — The  most  fascinating  question  in 
regard  to  migration  is  the  one  whose  solution  is  probably 
most  remote,  How  do  the  birds  find  their  way  ?  It  is  in 
agreement  with  scientific  method  that  instead  of  giving  too 
much  time  to  speculation  on  this  theme,  we  should  devote 
years  of  patient  investigation  to  the  much  humbler  question, 
What  way  do  they  find  ?  After  years  of  devotion  to  the  less 
ambitious  question,  we  shall  probably  be  able  to  ask  the 
more  fascinating  question  in  some  more  hopeful  form. 

No  doubt  the  wonder  is  great  that  birds  return  from  the 
south  to  their  birthplace  in  the  north  ;  that  inexperienced 
young  birds  make  a  long  journey,  often  over-sea,  to  suit- 
able winter-quarters,  with  success  in  a  large  proportion 
of  cases  ;  that  they  keep  their  direction  in  the  dark  and  at 
great  heights,  and  while  flying  over  the  pathless  sea.  It 
is  true  that  there  are  many  failures,  a  crop  of  tragedies 
every  year,  a  never-ceasing  process  of  discriminate  and 
indiscriminate  elimination,  but  the  marvel  is  the  relative 


THE   INSURGENCE  OF  LIFE  181 

success  of  one  of  the  most  daring  of  life's  experiments. 
Let  us  glance  very  briefly  at  the  various  suggestions  that 
have  been  made  in  regard  to  the  way-finding.  (1)  It  has 
been  suggested  that  success  in  way-finding  may  be  due  to 
inherited  experience,  slowly  cumulative  from  generation 
to  generation,  enriched  and  specialized  by  individually 
minute  contributions.  There  is  probably  very  little  sound- 
ness in  this  suggestion,  for  we  have  no  secure  evidence  of 
the  direct  entailment  of  the  results  of  experience,  and  we 
find  it  difficult  to  state  what  content  the  experience  could 
have  in  the  case  of  birds  flying  by  night,  and  often  at  great 
heights,  and  across  the  sea,  as  so  many  do. 

(2)  An  attractive  theory  is  that  of  social  tradition,  and 
in  this  there  may  be  some  truth.     The  idea  is  that  those 
lead  well  one  year  who  followed  well  for  several  years 
before.     Ornithologists  are  not  quite  omniscient ;    there 
may  be  some  old  experienced  hands  amongst  that  rushing 
troup    of    youngsters.     But     the    difficulties    are    great. 
How  could  the  old  hand  become  experienced  in  the  matter 
of  a  night  journey  across  the  Mediterranean  ?     In  the  case 
of  the  cuckoo  there  does  not  seem  to  be  a  single  adult  left 
in  Britain  when  the  youngsters  begin  to  migrate.     But 
there  is  no  evidence  that  cuckoos  are  less  successful  migrants 
than  other  birds.     It  has  been  said  that  they  may  migrate 
with   their  foster-parents,  but  this,  if  true,  cannot  be  the 
whole  truth,  since  a  number  of  the  species  who  act  as 
foster-parents  are  non-migratory  birds. 

(3)  A  third  theory,  that  has  a  great  deal  to  be  said  for  it, 
lays  all  the  emphasis  on  sensory  acuteness.     Birds  have 
very  keen  senses   of  sight  and  hearing ;    the  migrants 
sometimes  follow  coast-lines,  river-valleys,  lines  of  islands, 
and  so  on.     But  it  is  quite  plain  that  this  cannot  be  the 


182  THE  WONDER  OF  LIFE 

whole  answer,  since  many  birds  migrate  by  night  and  at 
considerable  altitudes.  Nor  are  there  any  landmarks  in 
the  open  sea. 

(4)  The  fourth  suggestion  has  almost  certainly  a  high 
degree  of  soundness,  that  birds  have  in  a  sublime  degree 
'  a  sense  of  direction ',  which  is  expressed  in  two  forms — 
as  a  capacity  for  flying  continuously  in  a  definite  direction, 
and  as  a  capacity  for  '  homing  '.  In  regard  to  the  second 
form  we  have  some  data,  for  the  '  homing  '  powers  of  cats 
and  dogs,  cattle  and  horses,  are  well  known.  Even  when 
the  cat  is  put  in  a  basket,  and  taken  in  a  cab,  and  then  hi 
a  tram,  it  may  find  its  way  back.  It  is  true  that  we  do 
not  hear  very  much  of  the  cats  who  left  their  second  home 
and  did  not  return  to  their  first  home,  but  the  positive 
cases  are  very  interesting.  There  are  some  striking  facts 
to  which  we  shall  refer  in  the  chapter  on  Animal 
Behaviour,  which  go  to  show  that  if  a  hive-bee,  issuing 
from  the  hive,  be  caught  and  imprisoned  in  a  box  and 
put  into  a  pocket,  and  be  thus  transported  for  an 
intricate  half-mile,  and  then  released,  it  ascends  into 
the  air,  and  makes  a  '  bee-line  '  for  home.  The  '  homing  ' 
of  pigeons  is  also  a  familiarly  established  fact,  and 
the  value  of  it  is  not  lessened  by  knowing  that  the 
power  can  be  greatly  increased  by  training.  In  fact,  it 
seems  legitimate  to  suppose  that  birds  have  in  a  sublime 
degree  the  sense  of  direction  and  the  homing  faculty.  But 
all  that  we  can  say  is,  that  this  not  unwarranted  assump- 
tion makes  the  problem  of  way-finding  less  of  an  isolated 
riddle. 

A  Particular  Case. — A  story  that  may  well  excite 
admiration  is  that  of  the  Pacific  Golden  Plover  (Charadrius 
dominicus  fulvus),  large  numbers  of  which  winter  in  the 


THE  INSURGENCE  OF  LIFE  183 

Hawaiian  Islands,  which  are  about  2,000  miles  away  from 
any  continental  area.  Mr.  H.  W.  Henshaw  suggests  that  the 
islands  were  accidentally  discovered  by  storm-driven  waifs 
who  were  blown  out  to  sea  when  following  their  usual 
southward  migration  route  along  the  Asiatic  coast  in 
autumn.  In  any  case  the  islands  have  become  favourite 
wintering  grounds,  and  the  migration  to  and  fro  has  come  to 
be  a  regular  recurrence.  The  birds  leave  the  islands  in  spring 
in  very  good  condition  and  probably  fly  straight  on  across  the 
ocean,  without  feeding  or  resting,  till  they  reach,  it  may  be, 
the  Aleutians.  There  is  good  reason  to  believe  that  many 
of  the  Golden  Plover  breeding  in  Alaska  are  from  Hawaii, 
and  that  many  of  those  that  arrive  in  Hawaii  in  autumn 
have  been  in  Alaska.  '  It  thus  appears  ',  Mr.  Henshaw 
says,  '  that  thousands  of  birds,  large  and  small,  make  a 
2,000-mile  flight  from  Alaska  to  Hawaii  in  fall  and  return 
in  spring '.  The  flights  are  hazardous  and  many  are  lost, 
but  the  marvel  is  that  so  many  are  successful. 

'  What  at  first  might  appear  a  physical  impossibility — 
the  2,000-mile  flight  of  small  birds  across  an  ocean  highway 
without  a  single  landmark  and  with  only  the  friendly  winds 
to  guide  them,  if  indeed  they  utilize  these  as  guides — is 
not  only  possible,  but  the  feat  is  accomplished  annually 
by  many  thousands  of  individuals,  and  apparently  with  no 
stops  for  rest  or  food.  The  wonder  of  it  is  increased  when 
we  realize  that  these  annual  flights  are  undertaken  solely 
for  the  purpose  of  making  a  sojourn  of  a  few  brief  weeks  in 
Alaska  to  nest  and  rear  their  young.' 

Mr.  Henshaw  falls  back  on  the  hypothesis  of  '  a  sense  of 
direction  tantamount  to  a  sixth  sense '.  The  confidence 
with  which  the  migrants  launch  out  from  Hawaii  into  the 
trackless  waste  certainly  gives  us  pause. 


1 84  THE  WONDER  OF  LIFE 

Even  if  we  postulate  that  they  know  how  to  make  a 
journey  that  they  have  made  before,  and  that  young  birds 
serve  some  apprenticeship,  there  rises  the  further  ques- 
tion, Why  do  they  launch  forth  at  all  ?  The  departure 
from  Alaska  in  autumn  is  obviously  intelligible,  they  must 
flit  or  starve  ;  but  why  do  they  leave  Hawaii  ?  There  is 
plenty  of  room  and  plenty  of  food,  and  some  American 
birds — a  stilt,  a  night  heron,  a  gallinule,  a  goose,  a  short- 
eared  owl,  and  a  buzzard — which  probably  came  as  waifs, 
like  the  Golden  Plover,  have  become  resident  Hawaiian 
birds.  Why  does  not  the  Golden  Plover  become  a  resident  ? 
The  probable  answer  is  a  purely  biological  one,  that,  as  Mr. 
Henshaw  suggests,  the  Golden  Plovers  were  originally 
Arctic  birds,  and  that  they  have  a  homing  impulse,  a 
constitutional  desire  to  return  to  their  cradle- country,  the 
Northern  paradise  from  which  the  ice  once  expelled  them. 
We  agree  with  this  observer  in  adopting  the  hypothesis  of 
an  organic  home-sickness  which  prompts  a  return  at  the 
breeding  season  to  the  original  headquarters  or  somewhere 
in  that  direction. 

Retrospect. — A  few  examples  may  be  as  effective  as 
many  thousands  to  illustrate  that  quality  of  living  creatures 
which  every  one  in  some  instance  or  other  has  had  occasion 
to  admire.  When  we  watch  the  literal  legions  of  starlings 
circling  over  their  resting-place  on  Cramond  Island  in  the 
Firth  of  Forth,  or  the  living  cataract  of  guillemots,  razor- 
bills, and  puffins  that  descends  from  one  of  the  great  bird- 
bergs  of  the  North  when  we  rattle  the  oars  in  the  boat,  or 
a  swarm  of  locusts  in  South  Africa  darkening  the  sky  with 
a  thick  curtain  of  wings,  we  feel  the  insurgence  of  life. 
When  we  watch  the  flying-fishes  rise  in  hundreds  before  the 
prow  of  the  steamer,  like  grasshoppers  in  a  meadow ;  or 


THE  INSURGENCE  OF  LIFE  185 

the  storm-petrels  flying  over  the  waves  with  dangling  feet, 
never  touching  land  except  to  nest ;  or  the  salmon  leaping 
the  falls  ;  or  the  elvers  on  their  journey  up-stream,  we  feel 
again  the  insurgence  of  life.  When  we  gaze  at  the  cut 
stem  of  the  Sequoia,  which  was  a  sapling  a  few  years  after 
the  Fall  of  Rome,  we  are  in  presence  of  another  form  of  the 
Will  to  Live.  When  we  consider,  as  we  have  been  doing, 
the  fascinating  wonder  of  bird-migration — one  of  the  great 
adventures  of  life — we  have  a  fine  expression  of  the  same 
quality.  But,  most  of  all,  when  we  come  to  reckon  with  the 
history  of  organisms,  when  we  see  life  slowly  creeping 
upwards  through  the  ages,  adapting  itself  to  every  niche 
of  opportunity,  expressing  itself  progressively  with  in- 
creasing freedom  and  fullness,  do  we  realize  what  is  meant 
by  insurgence. 


CHAPTER  IV 

THE  WAYS  OF  LIFE 
(MODES  OF  ANIMAL  BEHAVIOUR) 

'Bacb  of  bet  works  bas  an  essence  of  its  own ;  eacb  of  ber 
pbenomena  a  special  characterisation;  and  set  tbeic  diver* 
sitg  is  in  units.  .  .  .' 

'Sbe  bas  alwap.8  tbougbt  and  always  tbtnfcs ;  tbougb  not 
as  a  man,  but  as  "Mature.  Sbe  broods  over  an  allscompre* 
bending  idea,  wbicb  no  searching  can  find  out.  .  .  .' 

« Sbe  creates  needs  because  sbe  loves  action.  Wondrous ! 
tbat  sbe  produces  all  tbis  action  so  easily.  JEverp.  need  is  a 
benefit,  swiftly  satisfied,  swiftly,  renewed.  jEverg  fresb 
want  is  a  new  source  of  pleasure,  but  sbe  soon  reacbes  an 
equilibrium/ 

4 Sbe  bas  neither  language  nor  discourse;  but  sbe  creates 
tongues  and  bearts,  bp.  wbtcb  sbe  feels  and  speaks.' 

— Goethe's  Aphorisms,  translated  by  Huxley. 

What  is  Animal  Behaviour  ? — Behaviour  of  the  Lower  Animals : 
— Tropisms  and  more  than  Tropisms — The  Study  of  Animal 
Instinct — Instances  of  Instinctive  Behaviour — The  Tale  of 
the  Black  White  AmW-Specialized  Character  of  Many  Instincts 
— Limitations  of  Instinct — Some  Difficult  Phenomena  :  '  Feign- 
ing Death  ',  '  Bluffing ',  '  Homing ',  '  Masking ' — Intelligent 
Behaviour — Instinct  and  Intelligence— Educated  Animals. 

THERE  can  be  no  doubt  that  investigators  of  animal 
behaviour  during  the  last  quarter  of  a  century  have 
been  much  less  generous  than  their  predecessors,  and  that 
they  have  in  their  parsimony  greatly  advanced  our  under- 
standing.    For  it  is  an  important  rule  in  science  to  make  the 
186 


THE  WAYS   OF  LIFE  187 

most  of  the  simpler  factors  before  calling  in  the  aid  of  the 
more  recondite.  The  danger  lies  in  going  too  far  in  this 
direction,  trying  to  force  upon  facts  a  simplicity  which 
does  not  fit  them. 

The  older  naturalists  were  inclined  to  be  too  anthropo- 
morphic in  their  view  of  the  lower  animals,  reading  the  man 
into  the  beast  without  scruple,  and  accepting  anecdotes 
of  animal  intelligence  on  their  face  value  without  criticism. 
It  was  often  very  pleasing,  this  interpretation  of  animals 
as  homunculi  of  the  '  Brer  Rabbit '  type,  with  all  the 
human  faculties  in  miniature,  except  perhaps  reason ;  but 
it  was  not  good  science.  The  reaction  came  inevitably, 
and  about  1900  we  find  investigators  like  Bethe,  Beer,  and 
Uexkiill  declaring  that  it  was  time  for  biologists  to  give 
psychology  a  rest  and  to  tackle  the  problems  of  animal 
behaviour  biologically.  And  some  have  been  so  satisfied 
with  their  biological  interpretations — in  terms  of  nerve  and 
muscle,  protoplasm  and  its  metabolism — that  they  have 
put  '  the  animal  mind  '  entirely  on  the  shelf,  for  certain 
sections  of  the  animal  kingdom  at  least. 

WHAT  is  ANIMAL  BEHAVIOUR  ? 

Metabolism. — The  living  creature  is  always  undergoing 
change,  even  when  it  rests  ;  for  life  is  essentially  activity. 
Only  in  states  of  '  latent  life  '  and  the  like  does  the  ceaseless 
combustion  and  stoking,  waste  and  repair,  running- down 
and  winding-up,  come  to  an  approximate  standstill — 
from  which  it  is  easy  to  pass  into  death.  But  the  ceaseless 
metabolism  is  not  what  is  meant  by  behaviour. 

Everyday  Functions. — In  every  animal  there  are 
five  everyday  functions  or  activities.  There  are  what  Sir 
Michael  Foster  called  the  two  '  master-activities '  of 


i88  THE  WONDER  OF  LIFE 

movement  and  feeling,  or  contractility  and  irritability, 
connected  with  the  muscular  and  nervous  systems  respec- 
tively, if  these  are  differentiated.  These  two  master- 
activities  make  life  worth  living.  To  keep  them  a-going 
there  are  the  auxiliary  functions  of  (a)  nutrition  including 
the  ingestion,  digestion,  and  absorption  or  final  incorpora- 
tion of  nutritive  material ;  (6)  respiration,  including  the 
absorption  of  oxygen,  which  may  almost  be  called  a 
gaseous  food,  to  keep  the  vital  combustion  a-going,  and 
the  elimination  of  carbon  dioxide,  which  is  a  gaseous  waste  ; 
and  (c)  excretion,  or  the  filtering  out  of  the  nitrogenous 
waste.  Now  these  five  everyday  functions  are  the  condi- 
tions of  behaviour  ;  yet  behaviour  means  something  more. 
In  the  same  way,  the  periodic  functions  of  growth  and 
reproduction  may  be  said  to  condition  behaviour,  but  they 
do  not  necessarily  involve  it. 

The  beating  of  the  heart  is  a  very  vigorous  activity, 
going  on,  as  we  say,  '  automatically '.  It  is  in  reality,  of 
course,  very  subtly  controlled  by  the  nervous  system,  and 
can  adjust  itself  to  varying  conditions  within  the  body. 
We  may  take  it,  however,  as  a  good  type  of  automatic 
internal  activities,  such  as  the  respiratory  movements 
and  the  quiet  work  of  liver  and  kidneys  also  illustrate. 

Reflex  Actions  of  Parts  of  the  Body. — When  we 
quickly  draw  away  our  finger  from  a  hot  surface,  or  close 
our  eye  against  an  approaching  ball,  or  cough  when  a  crumb 
of  bread  threatens  to  go  the  wrong  way,  we  are  illustrating 
relatively  simple  reflex  actions  of  parts  of  the  body.  A 
stimulus  from  the  outer  world  affects  a  sensory  nerve,  a 
message  passes  to  the  central  nervous  system,  and  a 
response  quickly  passes  down  a  motor  nerve,  commanding 
a  muscle  or  several  muscles  to  move.  In  essence,  reflex 


THE  WAYS    OF   LIFE  189 

actions  involve  (1)  a  receptor  of  a  stimulus — a  sensory 
or  perceptory  nerve-cell — from  which  impulses  pass  in  to 
the  central  nervous  system,  (2)  a  '  motor  '  nerve- cell  which 
connects  the  central  nervous  system  with  a  muscle  or 
a  gland,  and  (3)  between  these  two  a  '  communicating ' 
nerve- cell  connecting  them  within  the  nervous  system.  The 
three  structural  units  taken  together  constitute  a  reflex  arc, 
but  in  actual  fact  reflex  actions  are  always  more  complex 
than  this  diagrammatic  analysis  suggests  and  cannot  be 
isolated,  except  in  theory,  from  other  reflexes  to  which  they 
are  linked. 

When  a  single-celled  organism  contracts  itself  or  draws 
away  from  a  stimulus — the  simplest  sort  of  response  that  a 
living  creature  can  make — it  seems  most  convenient  to  use 
the  term  reaction,  keeping  the  term  reflex  action  for  multi- 
cellular  animals  in  which  there  are  differentiated  elements 
forming  a  reflex  arc.  From  simple  reflex  actions,  such  as 
drawing  the  finger  away  from  a  hot  object,  there  is  a 
graduated  series  leading  on  to  such  complicated  reflex 
actions  as  coughing  and  sneezing  and  sucking. 

Reflex  actions  require  no  attention,  no  will,  no  con- 
sciousness, no  brain  ;  they  are  invariable  reactions  of  parts 
of  the  body  to  a  particular  stimulus,  and  depend  upon  pre- 
established  structural  arrangements  and  functional  sensi- 
bilities. It  seems  convenient  to  admit  that  they  hardly 
rise  to  the  level  of  behaviour,  for  that  term  implies 
that  the  organism  as  a  whole  is  an  agent  and  that  it 
exhibits  a  concatenated  series  of  actions.  In  behaviour 
there  is  a  more  or  less  effective  succession  of  adjust- 
ments of  the  whole  creature.  That  the  links  of  the 
chain  may  be  reflexes,  is  a  view  held  by  many  investi- 
gators. 


190  THE  WONDER  OF  LIFE 

Above  reflex  actions  of  parts  of  the  body  may  be  ranked 
a  series  of  movements — often  called  tropisms — such  as 
movements  towards  the  light  or  away  from  it,  towards 
warmth  or  away  from  it,  towards  one  chemical  substance 
and  away  from  another. 

Then  comes  the  great  range  of  instinctive  behaviour, 
differing  in  a  broad  way  from  reflexes  and  tropisms  in  its 
greater  complexity  of  concatenation,  differing  in  a  broad 
way  from  intelligence  in  its  fixedness  and  in  its  indepen- 
dence of  experience.  That  it  is  very  frequently  influenced 
by  intelligence  is  generally  admitted. 

The  higher  grade  of  behaviour  which  we  call  intelligent 
is  marked  by  conscious  control,  by  learning,  by  profiting 
from  experience,  by  '  perceptual  inference  ',  and  often  by 
experimenting.  In  the  individual  life-time  a  piece  of 
behaviour  which  required  intelligent  control  to  start  with 
may  by  dint  of  repetition  cease  to  require  this  and  become 
habitual. 

In  some  human  actions  there  is  a  control  of  behaviour 
in  reference  to  general  ideas,  there  is  '  conceptual '  instead 
of  '  perceptual '  inference,  and  to  this  the  term  rational 
conduct  should  be  restricted. 

Behaviour  looked  at  without  Analysis. — Before  going 
further,  it  may  be  useful  to  look  at  the  general  business  of 
animals,  without  raising  any  of  the  very  difficult  problems 
regarding  the  relative  status  or  significance  of  different 
kinds  of  behaviour.  What  is  it,  on  the  whole,  that  animals 
busy  themselves  with  ?  We  must  answer,  with  Prof. 
M.  F.  Guyer,  that '  Animals,  from  their  own  point  of  view, 
have  two,  and  only  two,  occupations  in  the  world.  These 
are  (1)  to  care  for  themselves,  and  (2)  to  care  for  their 
offspring.  Consequently,  every  important  thing  to  be 


THE  WAYS  OF  LIFE  191 

seen  about  an  animal  has  to  do  with  one  or  the  other  of 
these  pursuits '. 

Thus  we  see  animals  seeking  for  food,  storing  it,  making 
shelters  and  homes,  adjusting  themselves  to  the  inanimate 
world,  e.g.  in  migration  and  concealment ;  adjusting  them- 
selves to  other  creatures,  e.g.  in  combat  and  flight ;  seeking 
and  finding  mates,  preparing  for  the  young,  feeding  and 
otherwise  caring  for  the  young,  and  so  on.  There  may 
also  be  play  during  the  early  part  of  life,  courtship  at 
adolescence,  division  of  labour  within  a  community,  and 
co-operation  in  societary  enterprises,  such  as  building  a 
dam  or  going  on  a  slave-making  raid. 


BEHAVIOUR  OF   THE    LOWER   ANIMALS  :— TROPISMS   AND 
MORE  THAN  TROPISMS 

Tropisms. — In  the  lower  animals,  according  to  Loeb, 
Bohn,  and  others,  we  must  recognize  the  general  occurrence 
of  '  tropisms '  and  allied  reactions.  Every  one  knows 
that  plants  growing  in  a  window  bend  towards  the  light, 
and  this  is  said  to  come  about  automatically,  simply 
because  the  side  away  from  the  light  grows  more  quickly. 
We  do  not  need  to  suppose  that  the  plant  longs  for  the 
light.  In  the  same  way  animals  may  move  towards  the 
light  without  '  willing '  to  do  so.  Prof.  Jacques  Loeb 
has  explained  what  happens.  When  the  light  comes  from 
one  direction  and  strikes  one  eye,  it  sets  up  chemical  pro- 
cesses in  one  eye  which  are  different  (e.g.  quicker)  than  those 
in  the  other.  But  this  affects  the  nerves  and  muscles  of 
the  illumined  side  and  the  creature  moves  towards  the 
light.  For  it  is  usually  a  bilaterally  symmetrical  animal,  and 


192  THE  WONDER   OF  LIFE 

it  is  more  comfortable  for  it  to  have  its  chemical  processes 
in  equilibrium,  and  its  two  eyes  equally  illumined. 

Tropisms,  then,  are  obligatory  movements  which  result 
from  a  difference  in  the  role  of  chemical  processes  on  the 
two  sides  of  the  plane  of  symmetry.  Thus  we  have 
phototropisms,  or  obligatory  reactions  in  relation  to  a 
light  stimulus,  the  creatures  sometimes  moving  towards  it, 
like  some  moths,  caterpillars,  and  fishes,  which  are  said 
to  be  positively  heliotropic ;  and  sometimes  away  from 
it,  like  earthworms,  maggots,  and  freshwater  Planarians, 
which  are  said  to  be  negatively  heliotropic.  In  the  case  of 
fixed  animals,  like  sedentary  worms,  the  reaction  may  be 
simply  a  bending  towards  or  away  from  the  light. 

Similarly,  there  are  tropisms  in  relation  to  gravity 
(geotropism),  in  relation  to  currents  or  pressures  (rheo- 
tropism),  in  relation  to  diffusing  chemical  substances  and 
odours  (chemotropism),  in  relation  to  contact  with  surfaces 
(thigmotropism),  and  so  on.  In  all  cases  the  reaction  is 
obligatory  and  the  tendency  of  the  reaction  is  to  secure 
physiological  equilibrium.  As  we  ascend  the  scale  of 
being,  tropisms  are  often  caught  up  along  with  more  complex 
activities,  but  in  many  of  the  lower  animals  they  can  be 
studied  more  or  less  by  themselves. 

Some  observations  by  Davenport  Hooker  on  newly- 
hatched  Loggerhead  Turtles  illustrate  what  is  meant  by 
an  inborn  tropism.  The  babies  move  away  from  red, 
orange,  and  green,  but  move  towards  transparent  or 
opaque  blue.  It  is  probable,  at  any  rate,  that  this  helps 
them  to  reach  the  sea,  which  is  their  home,  though  they 
are  born  ashore.  After  entering  the  water  they  swim  out 
to  sea,  perhaps  attracted  by  the  darker  blue  of  the  deeper 
water.  In  a  large  sand-pit,  from  which  the  ocean  was 


THE  WAYS   OF  LIFE  193 

invisible,  they  did  not  move  in  any  definite  direction, 
and  the  control  experiments  showed  that  their  behaviour 
was  not  affected  by  the  sound  or  smell  of  the  sea. 

DIFFERENTIAL  SENSITIVENESS. — Associated  with  tro- 
pism,  is  the  phenomenon  of  '  differential  sensitiveness ',  to 
which  Loeb  and  Bohn  have  attached  great  importance. 
An  animal  which  is  moving  towards  the  light  comes  to  a 
shadow ;  it  may  cross  it,  it  may  come  to  a  standstill,  it 
may  recoil,  but  usually  it  tends  to  rotate  through  180°  and 
to  proceed  for  a  time  in  the  opposite  direction.  The  same 
phenomenon  is  observed  in  relation  to  gravity  and 
chemicals  diffusing  in  the  water. 

It  is  remarkable  to  see  a  tube- inhabiting  worm  in  an 
aquarium  instantaneously  draw  in  its  head  and  tentacles 
when  one  simply  puts  one's  hand  between  it  and  the  light. 
In  the  cells  of  these  beautifully  expanded  filaments  chemical 
processes  were  going  on  briskly  and  at  a  certain  rate  ;  by 
making  a  sudden  shadow  one  makes  a  sudden  change  in  the 
rate.  The  disturbance  stimulates  the  sensory  nerves,  and 
a  message  travelling  outwards  again  commands  the  muscles 
to  contract.  But  it  all  happens  so  quickly — before  one 
has  time  to  say,  '  Look  at  that ! ' 

Differentia]  sensitiveness  is  often  mixed  up  in  actual 
life  with  a  tropism-reaction.  Thus  Bohn's  experiments  on 
starfishes  led  him  to  conclude  that  these  brainless  creatures 
are  the  slaves  of  diverse  impulses,  whose  combination  may 
be  recognized  in  their  behaviour.  There  is  the  impulse 
due  to  the  immediately  preceding  state,  there  is  the 
trop ism-impulse,  and  there  is  the  rotatory  or  oscillatory 
impulse.  The  result  is  an  organic  (not  a  deliberate) 
compromise,  which  Bohn  says  may  be  almost  certainly 
predicted  in  given  conditions.  It  cannot,  however,  be 

O 


194  THE   WONDER  OF  LIFE 

compared  to  the  composition  of  forces — this  organic 
compromise — because  so  much  depends  on  the  physiological 
state  of  the  creature  at  the  time  being. 

Changes  of  Reaction  dependent  on  Internal  Condi- 
tions.— Modern  experimenting  has  made  clear  that  a  crea- 
ture's activity  at  a  given  time  is,  in  part,  dependent  on 
the  general  physiological  state  of  its  body,  apart  from  the 
activity  of  the  central  nervous  system.  And  the  physiolog- 
ical state  of  the  body  alters  with  functioning  and  environ- 
ment. A  well-known  instance  observed  by  Loeb  is  very 
striking.  The  caterpillars  of  Porthesia  chrysorrhcBa,  which 
emerge  from  hibernation  in  spring,  have  a  very  pronounced 
attraction  to  light  (positive  phototropism).  But  when  they 
have  eaten,  this  disappears  entirely,  and  does  not  reappear. 
The  physiological  state  of  the  body  has  been  thoroughly 
changed,  and  the  behaviour  likewise.  Loeb  also  notes  that 
when  the  male  and  female  ants  are  approaching  sexual 
maturity,  they  exhibit  an  intense  and  increasing  attraction 
to  the  light,  which  the  workers  do  not  show.  The  physio- 
logical state  of  the  body  has  been  altered  by  the  onset  of 
reproductive  maturity,  and  the  behaviour  is  correspondingly 
changed. 

After  an  animal  has  reacted  many  times  in  rapid  succes- 
sion to  the  same  stimulus,  it  ceases  to  do  so.  Some  active 
substance  in  the  sensory  cells,  or  in  the  nerve  cells,  or  in  the 
muscles,  has  been  used  up  for  the  time  being.  The  weak 
reactions  before  the  substance  was  quite  used  up  and 
before  it  has  been  properly  restored  have  been  put  down 
to  the  creature  remembering  that  it  had  been  fooled  these 
many  times.  But  it  is  almost  certain  that  this  is  quite 
wrong,  and  that  there  is  no  memory  involved  at  all. 
Cellular  memory  begins  when  there  is  some  more  or  less 


THE    WAYS   OF  LIFE  195 

lasting  change  or  registration  in  the  protoplasmic  organiza- 
tion. 

Changes  of  Reaction  dependent  on  External 
Changes. — A  small  crustacean  called  Gammarus,  very 
common  in  fresh  water,  where  it  plays  the  part  of  a  cleaner- 
up,  has  the  habit  of  avoiding  the  light.  It  frequents 
shaded  corners  and  gets  under  things.  To  avoid  using 
question- begging  terms,  we  say  that  it  is  negatively 
heliotropic.  Its  habitual  reaction  or  tropism  is  to  move 
away  from  the  light.  But  add  the  least  trace  of  acid  to 
the  water,  so  that  the  solution  is  no  stronger  than  T^§^  of 
one  per  cent.,  and  Gammarus  moves  towards  the  light. 
It  seems  almost  like  magic,  changing  the  creature's 
ingrained  habit  by  a  tiny  drop — not  of  some  potent  philtre 
— but  of  commonplace  acid  ! 

This  case  would  be  extremely  puzzling  if  it  stood  alone, 
but  there  are  related  facts  which  throw  some  light  on  it. 
Loeb  has  experimented  with  some  smaller  Crustaceans, 
Copepods,  which  do  not  seem  in  ordinary  circumstances 
to  be  much  affected  by  the  light.  When  they  are  put 
into  an  aquarium  lighted  from  one  side  only,  they  do  not 
behave  in  any  special  way.  But  if  some  water  rich  in 
carbonic  acid  be  poured  slowly  into  the  aquarium,  the 
scene  is  changed.  The  Copepods  become  positively  and 
strongly  heliotropic ;  they  form  a  group  in  the  brightest 
part  of  the  aquarium  and  dispose  themselves,  as  best  they 
can,  in  the  direction  of  the  light.  Loeb  suggests  that  the 
acid,  acting  as  a  catalyzer,  increases  the  amount  of  the 
material  affected  by  the  light  in  the  animal's  eye  from  a 
previously  minimal  and  negligible  quantity  to  a  quantity 
that  cannot  be  disregarded.  The  difference  between  the 
more  illumined  and  the  less  illumined  side  of  the  animal 


196  THE  WONDER   OF  LIFE 

becomes  appreciable,  and  the  animal  arranges  itself  so 
as  to  secure  chemical  equilibrium,  which  doubtless  spells 
comfort.  In  short,  the  addition  of  the  acid  has  quantita- 
tively increased  the  chemical  effects  of  the  light,  so  that 
it  ceases  to  be  negligible. 

Rhythmic  Movements. — The  story  of  the  little  green 
Planarian  worm,  Convoluta,  illustrates  the  combined  effect 
of  periodic  external  changes  on  the  one  hand  and  the 
internal  rhythms  of  the  body  on  the  other.  On  the  flat, 
sandy  beach  of  some  parts  of  Brittany,  the  small  worms 
come  up  in  crowds  when  the  tide  is  out,  and  form  green 
splashes  on  the  surface.  When  the  tide  comes  in  they 
retire  into  the  shelter  of  the  sand.  Their  movements  are 
synchronous  with  those  of  the  tide.  But  Bohn  has  shown 
that  the  Convolutas  in  a  quiet  aquarium  or  in  a  glass  tube 
behave  in  the  same  way ;  they  ascend  when  the  tide  goes 
down,  they  descend  when  the  tide  comes  in — though  they 
are,  of  course,  quite  away  from  all  influence  of  the  tides. 
What  is  still  more  remarkable  is  that  they  keep  time  with  the 
irregularities  of  the  tide.  Bohn  believes  that  the  alteration 
of  the  geotropism  from  plus  to  minus  may  be  associated 
with  the  alternation  of  relative  desiccation  and  relative 
hydration  during  the  periods  of  low  tide  and  high  tide. 
In  the  case  of  hermit-crabs,  however,  Anna  Drzewina 
observed  that  there  was  a  rhythmic  change  from  going 
towards  the  light  at  high  tide  and  from  the  light  at  low  tide, 
and  that  this  occurred  in  an  aquarium  where  they  were 
covered  with  water  all  the  time.  It  is  very  interesting 
to  find  that  a  rhythm  established  in  relation  to  external 
periodicities  persists  in  an  aquarium  where  there  is  uni- 
formity of  conditions.  A  beautiful  corroboration  of  the 
original  dependence  of  the  rhythm  on  the  tides  is  found  in  the 


THE  WAYS  OF  LIFE  197 

fact  that  hermit-crabs  from  the  Mediterranean,  where  there 
are  no  tides,  did  not  show  the  change  of  tropism  as  regards 
light,  but  were  always  positively  attracted  to  it.  According 
to  Bohn,  a  night  and  day  rhythm  has  been  to  some  extent 
established  in  the  constitution  of  some  sea-anemones,  which 
go  on  for  several  days  shutting  during  the  day  and  opening 
at  night,  although  they  are  kept  in  continued  darkness. 

There  are  internal  rhythms  in  the  body  whose  origin  is 
obscure,  e.g.  in  the  secretory  activity  of  the  kidney,  which 
is  at  its  minimum  at  about  9  p.m.  and  at  its  maximum 
in  the  early  hours  of  the  day.  Now,  as  Bohn  says,  we  do 
not  need  to  use  psychical  terms  in  referring  to  this,  and 
why  should  we  in  connexion  with  the  rhythms  exhibited  by 
shore  animals  in  relation  to  the  tides? 

Establishment  of  Tropisms. — In  many  cases  it  is 
plain  that  animals  improve  by  practice  ;  the  nerves  and 
muscles  become  fitter  by  exercise ;  the  creature  finds 
itself.  We  see  this  in  the  individual ;  apart  from  any 
learning  in  the  strict  sense  (by  association,  imitation,  and 
inference),  there  is  an  apprenticeship  of  cells,  tissues  and 
organs,  and  a  reward  of  increased  efficiency.  This  is  a 
matter  of  observed  fact.  What  remains  a  subject  of 
debate  is  whether  the  reward  of  individually  increased 
efficiency  is  in  any  way  entailed,  or  whether  racial  progress  is 
wholly  due  to  the  selection  of  the  fitter  germinal  variations. 
As  the  data  stand  at  present,  the  verdict  must,  we  think, 
be  given  in  favour  of  the  second  interpretation. 

Tropisms  are  hereditary  compulsions  to  certain  kinds  of 
movement,  and  it  is  a  thinkable  theory  that  the  particular 
combinations  of  them  that  occur  in  any  particular  animal 
express  the  result  of  a  long  process  of  selection.  It  is 
quite  true  that  the  tropisms  often  lead  the  animals  to 


198  THE  WONDER   OF  LIFE 

their  death,  e.g.  the  moths  to  the  candle,  and  that  some 
(e.g.  galvanotropism)  are  not  known  to  be  of  use  to  their 
possessors,  but  there  seems  much  evidence  that  the  com- 
bination of  tropisms  normally  exhibited  by  any  particular 
living  creature  is  well  adapted  to  the  ordinary  conditions 
of  its  life.  The  particular  combination  is  reasonably 
referred  to  the  work  of  selection. 

Beyond  Tropism. — The  question  which  one  would 
like  to  be  able  to  answer  is,  how  far  the  conception  of 
tropisms  and  the  like  suffices  to  cover  what  is  observed  of 
the  ways  of  the  lower  animals.  Is  tropism  all,  or  is  there 
a  gradual  emergence  of  something  more,  which  requires 
other  formulae  ?  Is  there  the  beginning  of  genuine 
behaviour  ?  When  a  monkey's  bonne-bouche  is  hidden 
in  a  vessel  of  a  particular  shape  and  colour,  which  is  then 
placed  among  other  vessels  of  other  shapes  and  colour, 
the  creature  proceeds  to  look  for  it  at  random.  But  as  the 
experiment  is  repeated  and  repeated,  with  due  precautions, 
the  monkey's  tentative  searches  become  fewer,  till  finally 
it  goes  straight  for  the  proper  vessel.  In  this  method  of 
trial  and  error  the  monkey  doubtless  uses  its  brains  ;  is  it 
possible  that  the  same  sort  of  method  may  be  exhibited 
by  animals  which  are  very  far  from  having  any  brains  at 
all? 

The  experiments  of  Jennings  are  in  favour  of  an  affirma- 
tive answer.  They  go  to  show  that  some  Infusorians 
practise  in  a  simple  way  this  method  of  trial  and  error, 
and  thus  make  a  step  beyond  tropisms.  The  Infusorian 
Oxytricha  fallax  was  observed  advancing  towards  a  warm 
region  of  the  water ;  it  recoiled,  turned  slightly  on  itself, 
and  advanced  again.  It  met  the  warmth  again  and 
repeated  the  same  reaction,  altering  the  direction  a  little. 


THE  WAYS  OF  LIFE  199 

This  happened  four  times  without  escape  from  the  warmth. 
Eventually,  however,  after  these  trials,  a  way  of  escape  was 
found.  There  are  some  who  do  not  accept  the  interpreta- 
tion that  Jennings  puts  upon  his  facts ;  but  every  one 
admits  that  his  facts  are  very  important  and  that  his 
interpretation  must  be  given  a  fair  hearing. 

Professor  Jennings  has  shown  that  the  Protozoon 
Stentor,  a  relatively  large  Infusorian,  reacts  to  a  precipita- 
tion of  powder  in  the  water  (1)  by  turning  aside  ;  or  if  that 
fails,  by  (2)  reversing  ;  or  if  that  fails,  by  (3)  contracting 
into  its  tube  ;  or  if  the  precipitation  continues,  by  (4)  shift- 
ing its  quarters  altogether.  So  far,  trial  of  different 
reactions,  three  of  which  were  ineffective,  though  in  other 
circumstances  any  one  might  have  been  a  perfectly  good 
answer.  But  the  point  is  that  when  Professor  Jennings, 
after  a  short  interval,  repeated  the  fall  of  powder,  the 
Stentor  began  with  the  fourth  answer.  It  had  learned 
something  from  its  experience. 

It  remains,  in  part,  a  matter  of  opinion,  but  to  us  it 
seems  impossible  to  describe  the  behaviour  of  Protozoa 
as  merely  due  to  tropisms.  What  they  do  is  not  always 
predictable,  they  seem  to  try  different  reactions,  they  seem 
to  learn  from  experience,  they  show  discrimination  or  selec- 
tion in  what  they  pursue  and  in  what  they  avoid.  Professor 
Jennings  goes  the  length  of  saying  :  '  In  no  other  group 
of  organisms  does  the  method  of  trial  and  error  so  com- 
pletely dominate  behaviour,  perhaps,  as  in  the  Infusoria '. 


THE  STUDY  or  ANIMAL  INSTINCT 

There  are  few  problems  that  have  been  more  discussed 
than  that  presented  by  the  instinctive  behaviour  of  animals, 


200  THE  WONDER  OF  LIFE 

and  it  remains — in  process  of  solution.  Almost  every 
modern  observer  admits  that  many  of  the  activities  of 
animals,  say  of  bees  and  wasps,  do  not  conform  well  with 
what  we  know  as  ordinary  intelligent  activities.  The 
observed  fact  is  that  there  is  a  different  '  tang '  about 
them.  The  problem  is  to  define  this  difference,  and  it 
may  be  that  one  of  the  reasons  why  we  find  this  so  difficult 
is,  that  we  are  ourselves,  predominantly,  creatures  of 
intelligence. 

In  early  days  the  problem  was  not  clearly  focussed. 
The  whole  of  animal  behaviour  was  slumped,  and  the  whole 
of  human  behaviour  was  slumped — two  quite  unscientific 
assumptions,  and  the  problem  was  to  find  the  difference 
between  them.  Of  course,  the  man  always  got  the  best 
of  it. 

Thus,  many  of  the  Greek  philosophers,  such  as  Plato, 
fixed  a  great  gulf  betwixt  the  thinking  man  and  the  impulse- 
driven  beast.  Man  had  reason  and  intelligence,  they  said  ; 
the  animal  had  sensations  and  impulses — only  an  anima 
sensitiva.  It  is  very  interesting  to  observe,  however, 
that  Aristotle,  while  ranking  animal  behaviour  at  a  much 
lower  level  than  man's,  recognized  clearly  that  it  was 
purposive. 

The  conception  of  instinct,  as  Nature-implanted  impulse, 
became  a  little  more  definite  among  the  Stoics.  They 
compared  animals  to  little  children  who  have  not  begun 
to  think.  Animals  have  sensations,  perceptions,  repre- 
sentations and  impulses,  they  said,  but  no  power  of  reason- 
ing. They  instanced  the  case  of  ducklings  hatched  and 
reared  by  a  hen,  which  show  an  inborn,  Nature-implanted 
impulse  or  instinct  to  make  for  the  water.  This  was  quite 
sound  in  its  way,  but  we  cannot  help  wondering  what 


THE  WAYS  OF  LIFE  201 

they  would  have  made  of  the  case  of  a  hen  which,  after 
several  successive  experiences  of  fostering  ducklings, 
involving  inter  alia  an  anxious  flight  on  to  a  stone  in  the 
middle  of  the  pond,  tried  to  lead  her  own  chicks  at  a  later 
date  to  the  water  ! 

In  the  Middle  Ages  and  later,  all  animal  activities  were 
slumped  together  and  ascribed  to  the  '  faculty  of  instinct ', 
and  all  human  activities  were,  with  equal  futility,  slumped, 
and  referred  to  the  '  faculty  of  reason '.  Instinct  was 
widely  regarded  as  a  divinely  implanted  capacity  of  doing 
purposelike  things  without  understanding  or  even  intending 
them.  This  vicious  parenthesis  of  '  faculty  psychology ' 
led  on  to  the  extreme  position  of  Descartes,  who  regarded 
animals  as  automatic  machines,  in  whose  workings  the 
psychical  substance  plays  no  part.  One  must  recognize 
that  in  this  extraordinary  view  he  had  a  clear  perception 
of  the  strangely  unplastic  and  stereotyped  character  of 
instinctive  behaviour.  But  he  did  not  realize  at  all  that 
many  animals  are,  apart  from  instinct  altogether,  very 
actively  and  acutely  intelligent. 

Through  a  number  of  notable  men,  and  in  different  ways, 
a  strong  reaction  set  in  against  the  Church  view  and  the 
Schoolmen's  view  of  animal  instinct.  It  was  pointed  out 
that  human  activities  could  not  be  defined  off  in  bulk 
as  different  in  kind  from  animal  activities.  It  was  shown 
that  some  forms  of  animal  behaviour  could  not  be  described 
except  as  intelligent,  but  that  there  was  another  kind  of 
animal  behaviour  on  somewhat  different  lines,  which  might 
be  called  instinctive.  The  reaction  gradually  led  to  the  posi- 
tion of  men  like  Biichner,  who  maintained  that  instinct 
was  a  term  for  the  hereditary  mental  predispositions 
towards  particular  sequences  of  behaviour — predispositions 


202  THE  WONDER  OF  LIFE 

which  were,  of  course,  embodied  in  the  particular  inborn 
brain- pattern  characteristic  of  the  organism  in  question. 
He  made  the  further  step,  which  seems  nowadays  so 
obvious,  of  recognizing  that  in  many  animals  instinctive 
behaviour  predominates,  while  in  others,  as  in  Man, 
intelligent  behaviour  predominates.  Thus  it  came  to  be 
no  longer  a  question  of  animal  behaviour  in  contrast  to 
human  behaviour,  but  of  two  different  modes  of  behaviour, 
both  of  which  may  be  illustrated  in  one  creature,  to  wit, 
instinctive  and  intelligent. 

Darwin's  contribution  comes  next.  With  his  charac- 
teristic common  sense,  he  was  quite  clear  that  in  animal 
behaviour  we  have  often  to  do  with  individual  experiment- 
ing and  inference — in  other  words,  with  the  exercise  of 
intelligence,  and  often,  also,  with  another  kind  of  capacity 
— instinct — '  implying  some  inherited  modification  of 
the  brain '. 

In  the  second  place,  taking  cases  like  the  instinct  of  the 
young  cuckoo  to  tumble  its  foster-parents'  offspring  out 
of  the  nest,  the  instinct  of  the  Ichneumon-fly  larvae  to 
devour  the  soft  body  of  the  caterpillar  in  which  they  find 
themselves  hatched,  the  instinct  of  the  cat  to  play  with  the 
mouse,  Darwin  argued  that  they  were  not  mysterious 
implantations,  but  growths,  accumulated  and  perfected 
by  Natural  Selection.  As  to  their  origin,  he  agreed,  on 
the  one  hand,  with  the  Lamarckian  school,  that  some  of 
them  might  have  arisen  through  the  transmission  of  intelli- 
gently acquired  habits ;  but,  on  the  other  hand,  he  laid 
most  emphasis  on  Nature's  sifting  of  the  inborn  variations 
which  are  continually  cropping  up.  Variations  in  structure 
are  of  frequent  occurrence,  and  so  are  variations  in  the 
responses  that  animals  make  to  external  stimuli.  New 


THE   WAYS  OF  LIFE  203 

answers  of  a  profitable  kind — variations  in  reflex  actions, 
for  instance — become  the  beginnings  of  new  instincts. 

After  Darwin  came  a  period  of  critical  discussion.  The 
two  chief  theories  of  the  origin  of  instincts  were  specialized 
and  pitted  against  one  another.  Spencer,  Haeckel,  Preyer, 
and  Wundt  were  prominent  among  the  supporters  of  the 
Lamarckian  interpretation — that  instincts  represent  the 
inherited  results  of  experience.  A  young  pointer  points 
because  its  ancestors  were  taught  to  point.  An  intelli- 
gently acquired  familiarity  with  a  certain  sequence  of 
actions  ingrains  itself,  first,  in  the  individual — as  a  habit, 
and,  second,  on  the  race — as  an  instinct,  the  intelligence 
lapsing.  But  other  instincts,  it  was  suggested,  may  have 
arisen  from  a  lower  level,  namely  from  reflex  actions,  such 
as  closing  the  eye  on  the  approach  of  a  missile,  or  the 
sucking  of  the  babe  when  it  is  put  to  its  mother's  breast. 
If  a  series  of  reflexes  occur  often  in  a  certain  routine, 
they  may  become  interlocked  with  a  certain  inevitableness, 
and  the  entailment  of  the  results  of  the  frequent 
repetition  of  such  a  sequence  may  give  rise,  so  the  theory 
ran,  to  an  instinct.  Both  forms  of  the  theory  postulate 
the  transmission  of  the  results  of  experience,  but  on  the 
first  supposition  the  experience  is  intelligent,  on  the  second 
it  is  simply  reflex. 

For  many  years  the  first  form  of  the  theory — that 
instinct  represents  lapsed  intelligence — held  the  field,  and 
it  is  certainly  a  very  attractive  interpretation.  Intelligent 
activities,  such  as  playing  the  piano,  become  by  long 
practice  habitual.  They  cease  to  require  concentrated 
intelligent  control ;  they  suffer  what  is  badly  called 
mechanization  ;  and  the  brain  is  left  freer  for  something  else. 
The  intricate  routine  is  somehow  ingrained  in  the  individual 


204  THE  WONDER  OF  LIFE 

memory ;  the  theory  is  that  in  the  course  of  generations 
the  capacity  of  going  through  the  routine  is  somehow 
ingrained  in  the  germ-plasm,  becoming  part  and  parcel 
of  the  inheritance.  On  this  attractive  view,  heredity  is 
the  racial  analogue  of  memory,  and  development  is  a  kind 
of  recollection. 

The  next  important  step  in  the  history  was  Weismann's 
critique  of  the  transmission  of  acquired  characters  or 
modifications.  These  may  be  defined  as  individually 
acquired  changes  of  bodily  structure,  which  are  directly 
due  to  changes  or  peculiarities  either  in  function  or  in 
environment,  and  which  so  transcend  the  limits  of  organic 
elasticity  that  they  persist  after  the  inducing  conditions 
have  ceased  to  operate.  That  these  are  of  common  occur- 
rence is  a  matter  of  everyday  observation;  that  they 
are  ever  transmitted  as  such  or  in  any  representative 
degree  has  not  yet  been  securely  proved  in  a  single  instance. 
It  is  likely  that  biologists  will  return  on  a  higher  turn  of 
the  spiral  to  a  recognition  of  the  importance  of  '  Nurture  ' 
in  evolution,  but  there  cannot  be  any  return  to  the  crude 
belief  in  the  transmission  of  individually  acquired  charac- 
ters that  was  general  before  Weismann's  criticism.  It  is 
very  difficult  to  see,  in  connexion  with  habit  for  instance, 
how  the  establishment  of  a  definite  brain- track  can  repre- 
sentatively affect  the  germ-plasm,  and  unless  it  does  that 
it  cannot  be  transmitted.  Thus,  if  Weismann's  critique 
be  sound,  it  forbids  the  assumption  which  is  fundamental 
to  the  Lamarckian  theory,  that  instincts  are  due  to  the 
inherited  results  of  experience.  Intellectual  ability  may 
be  transmitted,  for  it  is  primarily  due  to  a  germinal  varia- 
tion in  the  direction  of  increased  sagacity  ;  but  intellectual 
agility  due  to  practice  is  not  transmitted.  Thus,  Weismann 


THE  WAYS   OF  LIFE  205 

concluded  that  instincts  owe  their  origin — not  at  all  to 
experience  or  practice,  either  at  the  intelligent  or  the  reflex 
level,  but  wholly  and  solely  to  the  sifting  of  germinal 
variations.  The  pointing  quality  in  pointers  probably 
started  with  a  constitutional  variation  in  this  direction 
(there  are  analogous  cases  among  wild  hunting  animals). 
Man  took  advantage  of  this  and  strengthened  it  by  vigorous 
selection,  which  still  continues.  Moreover,  there  is  some 
individual  apprenticeship  still. 

Many  of  Weismann's  detailed  criticisms  must  be  kept 
in  mind  whatever  conclusion  is  arrived  at  in  regard  to 
the  nature  of  instinct.  He  referred,  for  instance,  to  the 
difficulty  raised  by  those  instinctive  actions  which  occur 
only  once  in  a  lifetime,  e.g.  the  young  bird  breaking  its 
way  out  of  the  imprisoning  egg-shell,  the  moth  escaping 
out  of  an  elaborate  cocoon,  the  nuptial  flight  of  the  queen- 
bee,  the  gall- wasp  laying  its  egg  with  such  precision  in 
the  very  heart  of  the  bud  of  the  wild  rose,  and  so  on  through 
a  long  list.  What  is  done  only  once  in  a  life- time  cannot 
become  a  habit ! 

Origin  from  Reflexes  and  Tropisms. — The  result 
of  Weismann's  criticism  was  to  concentrate  attention  on 
the  idea  of  the  origin  of  instincts  as  germinal  variations. 
As  this  view  presents  difficulties  to  many  minds,  let  us 
offer  some  illustration.  Every  now  and  then,  though  far 
too  rarely,  we  hear  some  one  say  of  a  child, '  he  has.  such 
peculiar  ways  of  his  own  ',  or  '  she  is  not  like  other  girls  '. 
That  means  a  certain  originality  or  idiosyncrasy,  a  new 
pattern ;  it  is  biologically  regarded  as  the  expression  of 
a  germinal  variation.  It  really  represents,  we  make  bold 
to  say,  an  experiment  in  self-expression  on  the  part  of 
the  creative  germ- plasm. 


206  THE  WONDER   OF  LIFE 

Now  these  germinal  variations,  whose  origin  is  another 
story,  find  expression  at  all  levels.  A  person  may  be 
born  with  a  chemical  variation  of  such  a  sort  that  even 
a  small  quantity  of  egg  in  his  food  acts  like  a  poison. 
Another  may  be  born  with  some  variation  in  the  eye  which 
leads  to  short-sightedness,  colour-blindness,  night-blind- 
ness, or  the  like.  Another  has  a  quite  unusual  sense  of 
locality  or  direction.  Another  is  a  musical  genius.  In 
short,  organisms  may  be  born  with  all  manner  of  constitu- 
tional variations  which  lead  them  to  respond  in  an  unusual 
manner  to  external  stimuli.  The  theory  of  instinct  to 
which  Weismannism,  for  instance,  leads,  is  that  instincts 
arise  from  within  as  germinal  variations,  that  those  which 
are  profitable  survive,  while  those  that-  are  very  disadvanta- 
geous (like  some  reversionary  instincts  in  man)  lead  to 
the  death  of  their  possessor.  Instincts,  as  M.  Marquet 
has  well  said,  are  '  inborn  inspirations '.  Their  origin  is 
confessedly  obscure — from  within  the  creative  germ- 
plasm — but  not  any  more  obscure  than  that  of  many  other 
inborn  variations,  such  as  any  form  of  genius,  or  any  novel 
departure  in  detailed  structure. 

Experiments  on  Instinct. — The  next  step  was  the 
establishment  of  the  experimental  study  of  instinctive  be- 
haviour, which  we  may  associate  in  particular  with  the  name 
of  Lloyd  Morgan.  Spalding  had  indeed  followed  the  same 
method  many  years  before,  but  his  observations  were 
somewhat  lacking  in  exactness.  What  Lloyd  Morgan  did 
was  to  incubate  the  eggs  of  fowls  and  some  other  birds 
in  the  laboratory,  so  that  he  could  study  the  behaviour 
of  the  young  away  from  any  influence  of  parental  education. 
He  was  in  this  way  able  to  demonstrate  the  instinctive 
character  of  some  capacities,  such  as  uttering  a  character- 


THE  WAYS   OF   LIFE  207 

istic  call-note  or  swimming  deftly  a  short  time  after  birth 
(in  the  case  of  coots).  In  the  case  of  the  young  water- 
hen  he  showed  that  the  capacity  of  diving  and  swimming 
under  water  was  also  thoroughly  instinctive,  but  might 
be  deferred  in  its  expression  for  a  long  time  until  the 
appropriate  liberating  stimulus  pulled  the  trigger.  Very 
instructive  was  his  demonstration  of  the  striking  absence 
of  instincts  that  one  might  have  expected  to  be  present. 
Thus,  the  young  chicks  to  whom  he  was  foster- parent  showed 
no  recognition  of  water  as  drinkable  material,  though  they 
would  take  drops  eagerly  from  a  finger  touching  their  bill. 
They  only  became  aware  of  water  as  water  after  they 
happened  to  wet  their  bills  by  pecking  their  toes  when 
standing  in  a  dish.  Then  they  immediately  drank  in 
the  usual  fashion.  The  chicks  had  never  seen  their  mother, 
of  course ;  but  it  was  perhaps  a  little  surprising  that  they 
paid  no  special  attention  to  her  clucking  outside  the  door. 
For  one  might  expect  innate  awareness  of  the  significance 
of  a  particularly  important  sound,  since  we  know  that  the 
capacity  of  producing  a  certain  call-note  is  in  some  cases 
innate  or  instinctive.  Professor  Lloyd  Morgan  also  found 
that  his  chicks  were  sometimes  innocent  enough  to  stuff 
their  crops  with  worms  of  red  worsted,  but  they  soon  knew 
better.  For,  the  important  outcome  of  the  investiga- 
tions was  that  the  chicks  make  up  for  their  paucity  of 
instincts  by  their  quick  intelligence — by  their  extremely 
rapid  educability. 

Lloyd  Morgan  worked  out  an  admirable  definition  : — 

'  Instincts  are  congenital,  adaptive  and  co-ordinated 
activities  of  relative  complexity,  and  involving  the 
behaviour  of  the  organism  as  a  whole.  They  are  similarly 
performed  by  all  like  members  of  the  same  more  or  less 


208  THE  WONDER  OF  LIFE 

restricted  group,  under  circumstances  which  are  either 
of  frequeDt  recurrence  or  are  vitally  essential  to  the  con- 
tinuance of  the  race.  They  are  to  be  distinguished  from 
habits  which  owe  their  defmiteness  to  individual  acquisition 
and  the  repetition  of  individual  performance '. 

Lloyd  Morgan's  work  marks  a  distinct  stage  in  the  study 
of  instinct.  The  experimental  method,  as  usual,  makes 
a  new  beginning.  His  work  has  been  continued,  but  only 
continued  by  other  investigators.  And,  leaving  aside 
entirely  some  important  experiments  on  animal  intelligence, 
we  may  say,  as  regards  the  history  of  the  investigation  of 
instinct,  that  the  two  new  steps  of  importance  are  concerned 
with  (a)  the  endeavour  of  Loeb,  Bohn  and  others  to  analyse 
particular  cases  of  instinctive  behaviour  into  combinations 
of  tropisms  and  the  like,  and  (6)  the  suggestion  of  Bergson 
that  instinct  expresses  a  particular  mo,de  of  knowledge, 
differing  from  intelligence  rather  in  kind  than  in  degree. 

INSTANCES  or  INSTINCTIVE  BEHAVIOUR 

When  we  pass  in  the  Animal  Kingdom  from  brainless 
types,  like  polyps  and  starfishes,  to  creatures  of  higher 
degree,  like  crabs  and  ants  and  spiders,  we  find  ourselves 
in  a  new  world.  There  are  tropisms  still,  and  there  is  differ- 
ential sensitiveness,  but  there  is  a  new  kind  of  behaviour 
much  more  complicated,  which  is  called  instinctive. 

When  a  shore-crab  is  carried  over  the  beach  and  then 
laid  down,  it  makes  for  the  sea  in  its  own  peculiar  sideways 
fashion.  Light  and  wind  and  slope  seem  to  have  no  effect ; 
it  makes  for  the  moisture  of  the  sea.  This  is  probably  a 
tropism,  perhaps  complicated  by  some  higher  capacity. 

When  a  worker-bee,  coming  out  of  the  hive  for  the  first 


THE  WAYS  OF  LIFE  209 

time,  flies  to  a  flower  which  it  has  never  seen  before,  and 
tackles  it  deftly,  collecting  pollen  and  nectar,  it  illustrates 
instinctive  behaviour.  We  say  that  it  does  its  work  '  as 
if  to  the  manner  born '  ;  and  it  is  characteristic  of  instinc- 
tive capacity  that  it  is  hereditarily  entailed. 

An  unhatched  lapwing  may  be  heard  saying  '  pee- wit ' 
from  within  the  egg.  This  is  its  distinctive  call-note,  and 
its  utterance  appears  to  be  instinctive — quite  independent 
of  instruction  or  imitation.  Chicks  reared  in  an  incubator 
have  the  usual  vocabulary.  This,  again,  is  characteristic 
of  instinctive  behaviour,  that  it  does  not  require  education 
or  example  or  practice,  though  it  may  be  improved  thereby. 
As  Dr.  Hans  Driesch  has  said,  instinctive  behaviour  is  '  a 
complicated  reaction  that  is  perfect  the  very  first  time.  ' 

The  mother  Sphex-wasp,  whose  behaviour  we  shall 
afterwards  discuss,  stocks  each  of  the  cells  in  her  nest  with 
three  or  four  paralysed  crickets.  On  the  under  side  of  one 
of  these  (turned  on  its  back)  she  fixes  an  egg,  out  of  which 
in  three  or  four  days  a  delicate  worm-like  larva  is  hatched. 
This  tiny  creature  bores  a  hole  through  the  cricket's  cuticle, 
makes  its  way  into  the  paralysed  body,  and  proceeds  to 
devour  the  tissues.  In  a  week  or  so,  having  attained  a 
length  of  twelve  millimetres,  it  goes  out  by  the  aperture  by 
which  it  entered,  and  proceeds  to  enjoy  another  cricket. 
In  about  twelve  days  it  has  eaten  all  its  larder.  Its 
behaviour  is  strikingly  instinctive. 

The  way  in  which  some  new-born  mammals  immediately 
proceed  to  suck  their  mother  illustrates  an  instinctive 
endowment.  '  Each  little  pig  the  moment  that  he  is  outside 
hurries  over  the  sow's  hind  legs,  and,  in  the  second  second 
of  his  outdoor  life,  has  a  teat  in  his  mouth '.  Newly -born 
pigs  also  show  instinctive  knowledge  of  the  significance 

f 


210  THE  WONDER  OF    LIFE 

of  the  sow's  grunting.  Spalding  put  a  young  pig  into 
a  bag  the  moment  it  was  born,  kept  it  in  the  dark  for  seven 
hours,  and  then  placed  it  near  the  sty,  ten  feet  from  where 
the  sow  lay  concealed. 

'  The  pig  soon  recognized  the  low  grunting  of  its  mother, 
went  along  outside  the  sty,  struggling  to  get  under  or  over 
the  lower  bar.  At  the  end  of  five  minutes  it  succeeded 
in  forcing  itself  through  under  the  bar  at  one  of  the  few 
places  where  that  was  possible.  No  sooner  in,  than  it 
went  without  a  pause  into  the  pig-house  to  its  mother, 
and  was  at  once  like  the  others  in  its  behaviour '. 

A  blind-folded  youngster  found  its  mother  almost  as 
well  as  one  with  its  eyes  free.  After  two  days  blindfolding 
it  required  only  ten  minutes'  practice  to  make  it  '  scarcely 
distinguishable  from  one  that  had  had  sight  all  along '. 

In  the  strict  sense,  birds  do  not  learn  to  fly,  though  their 
inborn  capacity  of  flying  is  improved  by  exercise.  Spalding 
put  five  unfledged  swallows  in  a  small  box  with  a  wire 
front,  and  hung  it  near  the  nest.  The  parents  fed  the 
offspring  through  the  wires,  and  the  young  birds  throve  as 
usual,  though  one  was  found  dead  just  as  it  became  fully 
fledged.  The  others  were  set  free  one  after  another.  Two 
of  them  were  perceptibly  wavering  and  unsteady,  and 
two  were  more  effective  from  the  first.  But  even  the 
less  endowed  flew  ninety  yards  right  away,  and  none  of 
them  knocked  against  anything.  In  a  subsequent  experi- 
ment one  of  the  newly-fledged,  newly -liberated  birds  per- 
formed almost  at  once  magnificent  evolutions  over  the 
beech  trees.  All  this  was  performance  without  practice, 
for  the  swallows  had  not  been  able  even  to  extend  their 
wings  in  their  narrow  prison. 

In  the  familiar  case  of  the  spider's  web,  there  is  no 


THE  WAYS   OF   LIFE 


211 


evidence 
that     the 
spinner  im- 
proves   by 
practice. 
T  h  e  fi  r  s  t 
web    made 
by     the 
spiderling 
has  all  the 
parts    seen 
in  the  web  made 
by     the     adult. 
Montgomery  has 
shown,  in  species 
of   Epeira,    that 
as    the     spiders 
grow    older    the 
thread    becomes 
thicker   and   the 
web  larger ;  there 
are  a  few  more 
radial  rays  and  a 
few    more    loops 
in  the  spiral,  but 
these  differences 
are      correlated 
with    the     in- 
creased     weight 
of  the  spider  and 
the       increased 
size  of  the  spin- 


FIG.  39. — Young  garden 
spiders,  moving 
around  their  nest, 
rising  and  sinking 
on  threads  of  silk, 
and  congregating 
in  a  central  mass. 
(After  Koesel.) 


212  THE  WONDER  OF  LIFE 

ning  organs.  There  is  more  material  to  work  with,  and 
the  web  is  a  little  more  substantial,  but  there  is  no  real 
change,  or  need  for  any. 

We  shall  take  two  or  three  instances  from  the  veteran 
entomologist,  Fabre,  whom  Darwin  called  '  that  inimitable 
observer ',  who  has  perhaps  got  nearer  the  intimate  life 
of  insects  than  any  one  has  done  since  the  days  of  Reaumur. 
Fabre  sees  Instinct  in  the  insect  world  looming  as  a  big, 
underivable  fact,  which  must  be  taken  as  given,  which 
cannot  be  explained  in  terms  of  anything  else,  either 
intelligence  or  reflex  action. 

Picture  the  ringed  Calicurgus  wasp,  which  first  stings 
its  captured  spider  near  the  mouth,  thereby  paralysing 
the  poison  claws,  and  then,  safe  from  being  bitten,  drives 
in  its  poisoned  needle  with  perfect  precision  at  the  thinnest 
part  of  the  spider's  cuticle  between  the  fourth  pair  of  legs. 

Looking  in  another  direction,  what  can  we  say  of  the 
mother  of  the  Halictus  bee  family,  who,  after  prolonged 
maternal  labours,  becomes  in  her  old  age  the  portress  of 
the  establishment,  shutting  the  door  with  her  bald  head 
when  intrusive  strangers  appear,  opening  it,  by  drawing 
aside,  when  any  member  of  the  household  arrives  on 
the  scene? 

The  solitary  digger  wasp,  Ammophila,  is  wont  to  drag 
caterpillars  to  the  living  larder  which  she  accumulates 
for  her  young.  The  victim  must  be  made  inert,  but  it 
must  not  be  killed.  The  Ammophila  first  and  quickly 
stings  the  caterpillar  in  the  three  nerve-centres  of  the 
thorax  ;  she  does  the  same  less  hurriedly  for  the  abdomen  ; 
and  then  she  squeezes  in  the  head,  producing  a  paralysis 
which  cannot  be  recovered  from  !  This  ghastly  but  wonder- 
ful manifestation  of  instinct  requires  no  noviciate,  it  is 


THE  WAYS  OF  LIFE  213 

perfect  from  the  first,  it  expresses  an  irresistible  inborn  im- 
pulsion, at  once  untaught  and  unteachable.  The  insect's 
achievements  are  due  to  '  inborn  inspirations  '.  They  look 
like  intelligence  ;  but  disturb  the  routine,  and  the  difference 
becomes  at  once  apparent.  To  instinct  everything  within 
the  routine  is  easy ;  but  the  least  step  outside  is  difficult. 

It  is  many  years  since  Fabre  described  the  behaviour 
of  the  Sphex  wasp  (S.  flavipennis  or  S.  maxillosus)  in 
stocking  a  larder  for  its  young.  It  makes  burrows,  each 
consisting  of  a  horizontal  porch,  a  sloping  main  shaft, 
and  off  this  three  or  four  horizontal  cells.  In  each  cell, 
the  wasp  places  an  egg  and  three  or  four  paralysed  crickets 
or  related  insects.  Each  cell  is  closed  when  it  is  filled, 
and  the  shaft  is  closed  when  the  storing  is  completed. 
Another  shaft  is  then  sunk. 

When  the  Sphex  catches  its  cricket  it  stings  it,  usually 
three  times,  in  three  different  strategic  points  in  the  nervous 
system,  the  result  being  that  the  cricket  is  incapable  of 
movement,  but  remains  alive  until  the  larvss  of  the  Sphex 
are  ready  to  devour  it.  When  the  Sphex  has  stung  the 
cricket,  it  grips  it  by  an  antenna  and  drags  it  or  flies  with 
it  to  the  mouth  of  the  burrow.  There  it  lays  it  down, 
and  proceeds  to  inspect  the  burrow  to  see  that  everything 
is  as  it  should  be.  If  everything  is  in  order,  it  comes 
up  again,  and  drags  the  cricket  with  it,  going  in  backwards. 
The  interesting  experiment  that  Fabre  made  was  to  remove 
the  cricket  while  the  Sphex  was  making  its  inspection  of  the 
burrow.  He  placed  it  at  a  short  distance.  The  Sphex, 
coming  up  again,  was  apparently  agitated  by  the  disappear- 
ance of  its  captive  and  sought  for  it  energetically.  Having 
found  it,  the  Sphex  drew  it  a  second  time  to  the  mouth 
of  the  burrow,  laid  it  down  again,  and  proceeded  to  inspect 


214  THE  WONDER  OF  LIFE 

afresh !  This  routine  was  repeated  no  fewer  than  forty 
times  in  succession,  and  the  apparent  compulsion  to  do 
things  always  in  a  given  order  is  evidently  strong. 
Although  the  burrow  had  been  so  often  inspected,  the 
Sphex  had  to  do  it  again,  when  it  brought  its  captive 
cricket  once  more  to  the  entrance. 

In  regard  to  a  nearly-related  East  Indian  wasp,  Eothney 
made  a  similar  experiment,  which  is  summarized  by  Dr. 
Sharp  (Cambridge  Natural  History,  vol.  6,  p.%  110). 

'  He  discovered  a  nest  in  process  of  construction,  and 
during  the  absence  of  the  mother-wasp  abstracted  from 
the  burrow  a  large  field-cricket  that  she  had  placed  in 
it ;  he  then  deposited  the  Orthopteron  near  the  cell.  The 
parent  Sphex,  on  returning  to  work,  entered  the  tunnel 
and  found  the  provision  placed  therein  had  disappeared. 
She  came  out  in  a  state  of  excitement,  looked  for  the  miss- 
ing cricket,  soon  discovered  it,  submitted  it  to  the  process 
of  malaxation  or  kneading,  and  again  placed  it  in  the  nest, 
after  having  cleared  it  from  some  ants  that  had  commenced 
to  infest  it.  She  then  disappeared,  and  Eothney  repeated 
the  experiment.  In  due  course  the  same  series  of  operations 
was  performed,  and  was  repeated  many  times,  the  Sphex 
evidently  acting  in  each  case  as  if  either  the  cricket  had 
disappeared  owing  to  its  being  incompletely  stunned  or 
to  its  having  been  stolen  by  ants.  Finally,  the  observer 
placed  the  cricket  at  a  greater  distance  from  the  nest, 
when  it  recovered  from  the  ill-treatment  it  had  received 
sufficiently  to  make  its  escape.  The  points  of  interest 
in  this  account  are  the  fact  that  the  cricket  was  only  tem- 
porarily paralysed,  and  that  the  wasp  was  quite  able  to 
cope  with  the  two  special  difficulties  that  must  frequently 
occur  to  the  species  in  its  usual  round  of  occupations '. 

Fabre's   experiment   certainly   shows    how    thoroughly 


THE  WAYS   OF  LIFE  215 

an  instinctive  animal  may  become  the  slave  of  routine. 
On  the  other  hand,  there  are  details  in  the  story  which 
suggest  that  the  routine  is  no  blind  automatism.  There 
was  the  energetic  searching  for  the  stolen  cricket — a 
variation  from  the  usual  routine.  It  seems  pushing  the 
law  of  parsimony  too  far  to  suggest  that  the  search  was 
simply  the  fussing  about  of  a  perplexed  wasp.  There 
was,  moreover,  an  incidental  experiment  made  by  Fabre. 
On  one  occasion  he  substituted  for  the  paralysed  cricket 
another  specimen  which  had  not  been  stung.  When  the 
Sphex  came  to  drag  it  in,  the  cricket  naturally  resisted,  and 
there  was  a  keen  struggle.  It  did  not  last  long,  however, 
for  the  Sphex  soon  leaped  on  its  victim  and  stung  it  thrice. 
It  is  possible  that  intelligence  took  the  reins  at  the  critical 
moment.  In  any  case,  there  was  no  automatism. 

Fabre  has  led  many  to  marvel  at  the  effective  way  in 
which  the  Sphex  wasp  stings  the  cricket  in  its  ganglia, 
and  drags  the  paralysed  victim  to  the  burrow,  and  this 
marvel  does  not  stand  alone.  But  Marchal  points  out  that 
the  instinct  is  not  so  fixed  or  perfect  as  Fabre  represented. 
Mistakes  are  sometimes  made ;  the  precision  of  the  fatal 
thrust  is  sometimes  at  fault ;  many  blows  are  often  given. 
The  spots  where  the  Cerceris  strikes  the  Halictus  are  those 
most  conveniently  reached  by  the  sting  ;  the  squeezing  of 
the  brain  is  because  the  Cerceris  likes  the  juice ;  and  the 
idea  that  the  mother  Bee-hunter  empties  the  dead  bee  of 
its  honey  because  that  would  give  the  carnivorous  larvae 
pains  in  their  stomach  is  altogether  too  anthropomorphic 
(see  p.  426). 

THE  TALE  OF  THE  BLACK  '  WHITE  ANT  ' 

Among  quaint  and  wonderful  insects  a  unique  place 
must  be  ceded  to  the  so-called  '  white  ants  '  or  Termites. 


216 


THE  WONDER  OF  LIFE 


They  are  not  related  to  the  true  ants,  differing  widely 
from  them  in  structure,  in  life-history,  and  in  their 
social  economy,  but  they  resemble  them  in  their  achieve- 
ments and  in  compelling  our  admiration.  They  are 
unique  among  insects  in  often  contributing  to  the  scenery 
of  the  lands  which  they  inhabit,  for  the  hills  or  termitaries 
many  of  them  construct  out  of  masticated  earth  are  often 
twice  a  man's  height  and  are  often  as  thick  as  mole-hills 
on  a  badly  infested  field.  Indeed  there  are  many  parts  of 
South  Africa  where  the  hard 
domes  of  the  termitaries  form 
perhaps  the  most  prominent 
feature  in  a  monotonous  land- 
scape. Like  the  true  ants,  they 
are  '  lords  of  the  sub-soil ',  but 
their  appetite  for  woody  stuffs 
gives  them  a  wider  grip  of  things, 
and  their  influence  on  human  life 
is  very  considerable.  Telegraph 
posts  and  the  like  have  to  be 
made  of  iron  to  resist  their 
jaws ;  the  legs  of  the  table  have 
to  be  insulated  on  earthenware 
cups ;  and,  as  the  late  Pro- 
fessor Henry  Drummond  said,  there  are  many  places 
where  it  is  dangerous  for  a  man  with  a  wooden  leg  to 
go  to  sleep  without  taking  special  precautions,  else  his 
artificial  member  will  be  a  heap  of  sawdust  in  the  morning. 
We  must  not  even  begin  to  discuss  the  work  they  do  in 
pruning  forest  trees  of  their  decaying  branches,  and  in 
aiding  the  earthworms  in  the  circulation  of  the  soil — liter- 
ally making  the  world  go  round.  For  as  they  greatly 


FIG.  40. — Worker  Termite, 
Termes  ceylonicus; 
enlarged.  (After 
Bugnion.) 


THE  WAYS  OF  LIFE  217 

dislike  the  light,  almost  without  exception,  they  build 
earthen  tunnels  as  they  go,  and  the  substance  of  these  is 
sooner  or  later  weathered  down,  and  is  carried  by  the  rain 
to  the  streams  and  thence  to  swell  the  alluvium  of  the 
distant  valley. 

Another  introductory  note  is  necessary  before  we  pass 
to  consider,  as  a  particular  illustration  of  instinctive 
behaviour,  the  ways  of  the  Black  Termite.  A  little 
must  be  said  of  the  Termites'  social  economy.  There 
is  a  striking  division  of  labour.  Besides  the  males  and 
'  queens ',  that  is  to  say,  the  parental  members  of  the 
community,  there  are,  in  many  cases,  supplementary 
'  kings  and  queens ',  kept  in  reserve  and  ready  to  replace 
the  others  in  the  event  of  emergency.  Then  there  is  the 
great  body  of  '  workers  ',  who  are  really  permanent  children 
of  both  sexes,  non-reproductive  individuals  who  do  not 
grow  up.  They  differ  therefore  from  the  '  workers  '  in  the 
bee-hive  or  the  ant-hill,  who  are  all  females,  though  they 
remain  in  normal  circumstances  non-parental.  Finally, 
besides  the  workers  in  the  Termite  community  there  are 
often  big- jawed  soldiers,  likewise  non-parental,  and  the 
intricate  division  of  labour  does  not  end  here.  But  let  us 
turn  to  the  tale  of  the  black  Termite  of  Ceylon,  the  Black 
'  White  Ant '  as  who  should  say — a  tale  which  we  owe 
especially  to  the  patient  observations  of  Professor  Escherich 
of  Tharandt  and  Professor  Bugnion  of  Lausanne. 

The  Black  Termite,  so  abundant  in  Ceylon,  is  certainly 
peculiar.  It  is  more  like  a  true  ant  than  a  Termite.  It 
resembles  the  black  wood-ant  (Lasius  fuliginosus)  in  colour, 
in  many  of  its  ways,  in  its  nest,  and  even  in  its  smell. 
The  nest  is  usually  in  a  hollow  stem — a  labyrinth  of  pas- 
sages hollowed  out  in  a  brown  or  black  wood-paper.  When 


218 


THE  WONDER  OF  LIFE 


the  observer  opens  a  nest,  '  there  streams  out  a  very  flood 
of  black  creatures,  soldiers  and  workers,  covering  his 
hands,  but  doing  him  no  harm.'  Some  of  the  workers 
are  trying  to  save  the  babies — who  are  not  of  course  theirs 
— by  carrying  them  in  their  mouths.  Sometimes  a  white 
baby  is  seen  sticking  on  to  the  big  head  of  a  soldier. 

Familiarity  can  surely 
never  breed  contempt  at  the 
spectacle  of  a  Black  Termite 
army  on  the  march  through 
the  jungle,  moving  quickly 
in  a  twisting  file,  it  may 
be  several  hundred  yards 
long,  or  four  inches  across, 
pressing  through  and  round 
and  over  a  multitude  oi 
obstacles,  hurrying  on  hour 
after  hour,  at  the  rate  of 
about  a  yard  in  a  minute, 

FIG.  41.— Worker  Termite,  Termes  making  tortuously  for  a 
definite  end — a  tree  covered 
with  lichens  where  they 
find  their  food  supply.  We  speak  of  an  '  army ',  but 
most  of  the  marching  Termites  are  '  workers ',  the  soldiers 
are  posted  on  each  side  of  the  file  and  often  move  very 
little.  The  wonder  of  the  spectacle  increases  when  it  is 
discovered  that  through  the  whole  army — among  soldiers 
and  workers  alike — there  is  no  vision  at  all.  The  effective 
march  of  the  blind  army  depends  wholly  on  exquisite 
senses  of  touch  and  smell,  which  appear  to  be  located  in 
the  antennae  or  feelers. 
Professor  Bugnion  found  a  convenient  small  colony  of 


convulsionarius ;     enlarged. 
(After  Bugnion  and  Popoff.) 


THE  WAYS   OF  LIFE  219 

the  Black  Termite  in  the  hollow  stem  of  a  Pandanus,  and 
was  able  to  transport  it  intact  to  his  hut,  where  it  was 
placed  on  a  table.  The  very  first  night  the  black  army 
made  a  sortie,  descending  a  table-leg,  and  visiting  a  cocoa- 
tree  about  three  yards  off.  They  returned  in  the  morning, 
and  some  of  them  carried  a  little  greyish  yellow  lichen  in 
their  mouths.  The  next  event  was  an  invasion  of  the  Ter- 
mite nest  by  a  band  of  true  ants  (Pheidologeton)  whose 
soldiers  have  particularly  big  heads.  These  proceeded  to 
carry  ofi  the  Termite  larvae,  and  in  spite  of  valiant  resistance 
would  have  succeeded  had  not  M.  Bugnion  played  the  part 
of  providence.  He  drove  away  the  intruders  and  put  the 
Termite  nest  in  a  more  secure  place.  When  night  fell  the 
blind  army  made  another  sortie,  the  details  of  which  were 
interesting.  The  workers  came  out  tentatively,  guarded 
by  lines  of  soldiers  ;  after  going  a  little  way  some  turned 
back  again,  as  if  to  instruct  the  main  body  ;  they  got  on 
to  the  track  of  the  night  before,  which  was  marked  by  traces 
visible  to  M.  Bugnion  and  probably  smellable  to  the 
Termites.  But  after  all,  the  sortie  was  a  failure  ;  they  did 
not  find  the  cocoa-trees. 

The  observer  formed  a  little  bridge  over  a  deterrent 
difficulty,  and  next  day  the  cocoa-tree  with  its  lichens 
was  covered  by  innumerable  workers.  They  went  about 
their  business  in  groups,  five  or  six  grated  off  the  lichen 
and  passed  it  to  a  carrier,  who  continued  to  collect  till  he 
had  as  big  a  packet  as  his  mouth  would  hold.  But  the 
return  was  concerted  and  orderly,  not  individual  or  hap- 
hazard. It  did  not  begin  until  the  soldiers,  who  had  been 
standing  all  the  while  at  attention,  gave  a  signal.  After 
a  little  moving  to  and  fro,  the  workers  formed  into  line, 
descended  the  tree,  and  made  for  home  in  two  great  bands. 


220  THE  WONDER  OF  LIFE 

The  so-called  '  soldiers '  play  a  very  important  role  as 
guides  and  scouts.  When  Escherich  broke  a  march  by 
making  a  little  gully  with  his  finger,  there  was  general 
disorganization  in  the  ranks  be- 
hind the  interruption,  and  the 
spectacle  was  seen  of  the  soldiers 
exerting  themselves  to  the  utmost 
to  restore  order  and  the  broken 
connexion.  They  are  also  scouts, 
searching  out  new  lines  for  forag- 
ing. '  Very  carefully,  step  by 
step,  just  like  cats,  they  slink 
forwards,  one  behind  the  other, 
and  if  the  foremost  detects  any- 
thing the  least  suspicious,  he 
draws  nervously  back,  pulling 

FIG.  42.-Soldier   Termite,    his    "  brave "     comrades     after 
Termes      convulsion-    him.' 
arius  ;  enlarged.    (After 

Bugnion  and  Popoff.)         Professor    Bugmon    acted    as 
war-correspondent    to  the  black 

army  from  December  18  till  March  8,  and  the  story  of 
the  goings  out  and  comings  in  is  of  great  interest  to  the 
serious  student  of  animal  behaviour.  We  cannot  do  more 
than  refer  to  a  few  of  the  observations.  The  importation 
of  a  second  colony  led  to  a  war  which  lasted  for  three  days, 
after  which  a  peace  was  concluded,  and  the  first  colony 
(which  had  no  queen  and  only  a  few  children)  joined  the 
second.  An  excursion  was  made  every  day  ;  fifteen  cocoa- 
trees  were  visited,  some  at  a  distance  of  15-20  yards  ;  five 
roads  were  established,  which  were  carefully  adhered  to. 
Occasionally,  however,  the  whole  army  got  lost,  failing  to 
find  the  track  after  they  left  the  tree,  and  long  detours 


THE  WAYS   OF  LIFE  221 

were  sometimes  made  before  they  got  right  again.  The 
sortie  usually  began  about  sun-down  (6  p.m.),  but  earlier 
if  it  was  a  dull  afternoon  ;  there  seemed  always  to  be 
hesitation  and  caution  at  first ;  a  number  of  soldiers  acted 
as  scouts,  discovering  the  best  tree  ;  and  there  was  always 
that  turning  back  of  certain  individuals  who  kept  the 
main  body  in  touch  with  the  advance  guard.  The  orders 
seemed  to  be  given  through  the  antennae  or  by  a  quivering 
of  the  whole  body.  The  retreat  usually  began  at  dawn 
and  lasted  for  four  or  five  hours.  Escherich  notes  that 
most  of  the  return  journeys  ended  about  nine  or  ten  o'clock 
in  the  morning.  Photographs  of  the  sortie  (taken  by 
magnesium  flashlight)  and  of  the  retreat  (taken  in  daylight) 
showed  that  the  long  troop  of  workers  marched  between 
two  lines  of  soldiers  who  kept  their  heads  turned  outwards. 
As  to  numbers,  Escherich  computed  that  a  vigorous 
band,  crowding  past  at  the  rate  of  about  600  in  a  minute, 
would  comprise  about  200,000  individuals.  Professor 
Bugnion  counted  about  a  thousand  to  a  yard,  and  as  the 
army  took  five  hours  to  file  past  at  the  rate  of  a  yard  per 
minute,  there  must  have  been  about  300,000  individuals. 
There  were  over  two  hundred  soldiers  to  every  thousand 
workers.  Professor  Escherich  has  shown  that  the  number 
of  soldiers  guarding  a  march  varies  greatly  with  the  danger. 
When  the  risks  are  great  the  soldiers  stand  within  an 
antenna-length  of  one  another  so  that  they  are  always  in 
touch.  One  morning  the  returning  troop  was  harassed 
by  the  little  true  ant  previously  mentioned.  Professor 
Bugnion  counted  two  hundred  soldiers  on  a  length  of  four 
feet  forming  at  a  critical  point  a  living  wall  covering  the 
retreat  of  the  black  workers.  It  may  be  noted  that 
the  species  here  dealt  with  does  not  eat  wood,  but  subsists 


222  THE  WONDER  OF  LIFE 

almost  wholly  on  lichens,  occasionally  adding  particles 
of  rotting  leaf  and  something  out  of  the  damp  black  soil. 
Professor  Escherich  watched  them  grazing  like  so  many 
cows  on  a  meadow  of  green  unicellular  Algae  growing,  as 
we  often  see  in  this  country,  on  damp  stones.  Occasion- 
ally the  same  observer  saw  a  few  workers  eating  up  every 
shred  of  a  deceased  comrade. 

Escherich  was  greatly  impressed  by  the  cleanliness  of  the 
Black  Termites.  Like  cats,  they  spend  a  good  deal  of 
time  over  their  toilet,  and  they  lick  one  another  all  over, 
washing  every  crevice  of  their  many -hinged  bodies.  Their 
mutual  aid  in  this  direction  reminded  him  often  of  mon- 
keys. Care  is  taken  to  keep  the  nests  very  clean,  and  the 
refuse  is  disposed  of  in  a  scrupulously  tidy  way.  The 
keen-eyed  observer  goes  the  length  of  suggesting  that  there 
are  special  sanitary  inspectors.  It  certainly  looks  very 
like  it. 

Some  of  the  trees  visited  by  the  Black  Termites  bear  the 
nests  of  a  well-known  tailor-ant,  Oecophylla,  which  is  three 
times  bigger  than  our  Termite  and  much  more  agile. 
When  the  Termites  arrived  there  was  of  course  a  bitter 
battle,  in  which  the  true  ants  almost  always  got  the  worst 
of  it.  Escherich  occasionally  saw  the  soldiers  lose  their 
presence  of  mind  and  fall  back  on  the  workers,  among 
whom  a  temporary  panic  resulted.  The  soldiers  have  big 
heads,  but  very  small  jaws,  and  the  puzzle  is  how  they 
can  fight  at  all.  Their  tactics  are  nothing  short  of  extra- 
ordinary. When  the  Oecophyllas  draw  near,  the  Termites 
squirt  full  in  their  face  drops  of  a  viscous  secretion  which 
appears  to  drive  the  true  ants  almost  crazy.  They  drop  to 
the  ground  and  continue  for  a  long  time  rubbing  their  faces 
against  stones  and  debris.  The  Termite  soldiers  resume 


THE  WAYS   OF  LIFE  223 

their  attitude  of  detached  immobility  and  the  workers 
go  on  with  their  lichen-gathering. 

It  may  be  safely  said  that  the  recent  observations  on  the 
Black  Termite  have  given  the  student  of  animal  behaviour 
some  material  of  unsurpassed  interest  and  have  raised 
some  deep  problems.  Perhaps  their  chief  general  interest 
is  in  their  illustration  of  somewhat  complex  social  life  on 
an  instinctive  basis,  and  in  their  corroboration  of  the  view 
that  instinct  and  intelligence  are  expressions  of  life  on  quite 
divergent  tacks  of  evolution,  differing  rather  in  kind  than 
in  degree.  But  on  any  interpretation  the  Black  '  White 
Ant  '  is  passing  wonderful. 


SPECIALIZED  CHARACTER  OF  MANY  INSTINCTS 

One  of  the  striking  facts  in  regard  to  instincts  is  that 
they  are  often  highly  specialized,  and  that  their  value 
depends  on  their  precision.  Let  us  give  two  or  three 
examples.  It  is  well  known  that  the  young  cuckoo,  while 
still  blind  and  naked,  will  eject  the  rightful  tenants  of  the 
nest  with  great  effectiveness,  just  as  if  it  understood  all 
about  it.  It  is  helped  to  get  rid  of  the  eggs  by  a  hollow 
on  its  back,  which  persists  for  eleven  days  or  so.  A  careful 
observer  of  the  ejection  of  a  partly-fledged  young  pipit 
from  a  nest  below  a  heather-bush  on  the  declivity  of  a 
low,  abrupt  bank  has  called  attention  to  the  purpose- 
like  way  in  which  '  the  blind  little  monster  made  for  the 
open  side  of  the  nest,  the  only  part  where  it  could  throw 
its  burthen  down  the  bank '. 

The  specific  character  of  instinct  is  finely  illustrated  by 
the  solitary  wasps,  which  store  food  in  their  nests  for  the 
future  grubs.  In  most  cases  each  species  of  wasp  has  her 


224  THE  WONDER  OF  LIFE 

own  particular  kind  of  prey,  which  she  knows  instinctively  ; 
in  most  cases  she  handles  her  prey  in  a  quite  distinctive 
way ;  in  most  cases  she  has  a  particular  routine  when  she 
arrives  at  her  nest.  The  behaviour  is  complex,  adaptive, 
specific  and  constant.  There  is  hereditary  awareness  of 
certain  things  (a  cognitive  disposition),  and  there  is  linked 
to  that  a  hereditary  impulsion  to  a  certain  routine  (a  cona- 
tive  disposition).  As  Dr.  McDougall  puts  it : — 

'  The  structure  of  the  mind  of  such  an  animal  must  be 
conceived  as  consisting  of  a  limited  number  of  innate  cog- 
nitive dispositions,  each  linked  with  a  conative  disposition  ; 
and  the  maintenance  of  the  single  cycle  of  activities,  which 
compose  the  life  history  of  the  adult  creature,  depends 
on  the  fact  that  the  exercise  of  each  conative  disposition 
produces  a  situation  which  excites  another  cognitive  dis- 
position, which  in  turn  sets  to  work  another  conative 
disposition,  and  so  on,  until  the  cycle  is  completed '. 

Professor  Lloyd  Morgan  relates  his  instructive  experience 
with  a  young  moorhen  which  he  had  hatched  in  an  incu- 
bator. It  swam  well,  but  it  would  not  dive.  One  day, 
however,  when  it  was  swimming  in  a  pool  it  was  suddenly 
frightened  by  a  boisterous  puppy.  '  In  a  moment  the 
moorhen  dived,  disappeared  from  view,  and  soon  partially 
reappeared,  his  head  just  peeping  above  the  water  beneath 
the  overhanging  bank '.  Suddenly,  and  without  warning, 
it  had  exhibited  a  characteristic  piece  of  behaviour,  and 
its  dive  was  absolutely  true  to  type.  The  diving  perform- 
ance was  obviously  something  novel  and  specific ;  it  did 
not  grow  out  of  the  swimming  on  the  surface. 

The  method  of  self-delivery  practised  by  the  unhatched 
chick  within  the  egg  used  to  be  regarded  as  a  sort  of  appren- 


THE  WAYS  OF  LIFE  225 

ticeship  to  the  future  pecking.     But  it  is  quite  different. 
As  Spalding  observed  : — 

'  Instead  of  striking  forward  and  downward  (a  move- 
ment impossible  on  the  part  of  a  bird  packed  in  shell  with 
its  head  under  its  wing),  it  breaks  its  way  out  by  vigorously 
jerking  its  head  upward,  while  it  turns  round  within  the 
shell,  which  is  cut  in  two — chipped  round  in  a  perfect 
circle  some  distance  from  the  great  end '. 

At  the  time  of  hatching  there  is  an  exaggeration  of  a 
special  muscle  which  afterwards  ceases  to  be  conspicuous  ! 

Some  of  the  cases  of  so-called  instinctive  reaction  are 
so  strikingly  specific,  so  definitely  related  to  particular 
circumstances,  that  one  is  certainly  prejudiced,  at  first  sight, 
in  favour  of  the  view  that  the  lessons  of  experience  are  in 
some  way  entailed.  Professor  Semon  cites  such  a  case 
from  Lenz's  Schlangen  und  Schlangenfeinde  (Gotha,  1870) 
— a  very  reliable  work.  Lenz  took  two  young  buzzards 
from  the  nest  and  reared  them.  They  killed  slow-worms 
and  ringed  snakes  carelessly,  but  they  were  in  a  most 
striking  way  excited  when  they  first  had  to  deal  with  an 
adder.  They  had  previously  devoured  pieces  of  adder's 
flesh  quite  greedily,  so  it  could  not  be  smell  that  pulled  the 
trigger  of  the  instinctive  excitement.  Moreover,  buzzards 
work  by  sight.  The  question  then  is,  What  was  it  that 
made  the  buzzards  treat  the  adder  in  a  way  entirely  different 
from  that  in  which  they  dealt  with  grass  snakes?  The 
same  kind  of  fact  was  brought  out  by  the  experiments 
made  in  the  London  '  Zoo ',  of  confronting  various  types 
of  mammals  with  venomous  snakes.  None  paid  any 
attention  to  the  apparition  except  monkeys,  who  showed 
unmistakable  symptoms  of  great  fear.  It  is  probable 


226  THE  WONDER  OF  LIFE 

enough  that  these  inborn  antipathies  of  higher  Vertebrates 
are  ingrained  at  a  higher  level  of  the  brain  than  instincts 
are. 

An  exceedingly  interesting  inquiry  has  been  well  begun 
by  Dr.  Louis  Robinson  in  his  Wild  Traits  in  Tame  Animals 
(1897) — an  inquiry  into  those  modes  of  behaviour  which 
seem  to  be  survivals  of  the  original  wild  life.  It  was  in 
the  pack  that  the  dog  organically  learned  to  signal  by  its 
tail,  to  guard  its  bone,  to  obey  orders,  to  watch,  and  so  on. 
As  Darwin  suggested,  the  turning  round  and  round  on 
the  hearthrug  may  be  connected  with  the  primitive  roving 
of  the  pack,  which  moved  from  place  to  place  and  found 
temporary  resting-places  for  the  night  among  the  long  grass. 
The  crime  of  sheep- worrying  is  a  recrudescence  of  old  ways. 
Shying  in  horses  may  be  in  part  a  relic  of  a  valuable  ances- 
tral instinct  to  swerve  suddenly  from  suspicious  movements 
of  snake  or  wild  boar  or  crouching  tiger  among  the  bushes 
and  reeds.  Wild  foals  run  with  their  mothers,  and  unto 
this  day  they  do  not  gorge  themselves  with  milk,  as  calves 
do.  Scotch  cattle,  taken  to  a  large  American  ranch,  hid 
their  calves  among  the  thick  herbage,  true  to  the  old  ways, 
for  the  wild  cows  hide  their  young  in  the  thickets  while 
they  go  to  graze  in  the  open.  The  angry  ewe  still  stamps 
her  foot — the  old  signalling  of  danger  on  the  mountain 
side.  We  laugh  at  the  sheep  as  they  go  in  file  and  jump 
in  succession  over  an  imaginary  obstacle  simply  because 
one  of  them  did  it  by  mistake,  but  they  are  acting  in 
accordance  with  one  of  their  oldest  and  most  useful  instincts. 
The  pigs  squeal  now  because  their  wild  ancestors  squealed 
to  summon  their  neighbours  to  help  them  against  a  bear ; 
they  grunt  now  because  it  was  by  grunting  that  their 
ancestors  kept  together  in  the  jungle  or  among  the  high 


THE  WAYS   OF   LIFE  227 

bracken.  This  and  that  interpretation  may  be  fallacious, 
but  there  is  no  doubt  as  to  the  profitable  nature  of  the 
inquiry. 

LIMITATIONS  OF  INSTINCT 

Wonderful  as  instinctive  achievements  are,  they  are 
much  more  limited  than  those  of  intelligence.  They  are 
tied  down  to  particular  forms  and  sequences,  and  even  a 
slight  change  or  dislocation  makes  them  futile.  A  good 
example  of  this  limitation  of  instinct  is  given  by  Fabre,  who 
states  that  when  the  nest  of  the  common  wasp  is  covered 
with  a  bell  glass,  the  imprisoned  insects  never  dig  a  passage 
out,  though  they  could  if  they  tried,  but  remain  cooped  up 
till  they  die.  Moreover,  although  stragglers  which  had 
been  left  outside  will  actually  dig  their  way  in,  they  have 
not  wit  enough  to  show  their  fellows  the  way  out,  nor 
even  to  make  their  own  escape  again.  Instinct  is  always 
fatalistic. 

The  mason  bee  makes  a  mortar  nest  with  a  lid,  through 
which,  at  the  proper  time,  the  grub  cuts  its  way.  Put 
on  a  little  paper  cap  in  actual  contact  with  the  lid,  and  the 
grub  has  no  difficulty  in  cutting  through  the  extra  layer. 
But  if  the  covering  cap  be  fixed  on  just  a  little  way  above 
the  natural  lid,  not  in  contact  with  it,  the  grub  emerging 
into  the  closed  interval  between  the  lid  it  has  cut  through 
and  the  artificial  covering  cap,  can  do  no  more,  and  dies. 
It  could  cut  its  way  through  with  the  greatest  of  ease,  but  it 
cannot.  For  when  it  has  emerged  through  the  first  lid 
it  has  done  all  its  cutting,  and  it  cannot  repeat  it.  So,  the 
routine  having  been  disturbed,  it  dies  in  its  paper  prison, 
for  lack  of  the  least  glimmer  of  intelligence. 


228  THE   WONDER   OF  LIFE 

Similarly,  when  Fabre  wickedly  joined  the  front  end  of  a 
file  of  procession  caterpillars  to  the  hind  end,  they  went 
on  circling  round  and  round  the  stone  curb  of  a  big  vase 
in  the  garden,  day  after  day  for  a  week,  covering  persist- 
ently many  futile  metres.  As  Fabre  said  :  '  Us  ne  savent 
rien  de  rien '. 

Alfred  G.  Mayer  and  Caroline  G.  Soule  made  some  inter- 
esting experiments  on  the  caterpillars  of  the  milk-weed 
butterfly  (Danais  plexippus).  Thus  they  observed  that 
once  the  caterpillars  have  started  eating,  they  may  be 
induced  to  eat  substances  which  they  would  never  have 
begun  with.  Although  they  are  not  receiving  the  proper 
stimulus,  they  cannot  stop.  This  tendency  to  continue 
activity  '  in  the  face  of  a  non-stimulus '  is  called  '  the 
momentum  of  the  reaction '.  Another  interesting  point  is 
the  shortness  of  their  associative  memory.  If  a  '  distasteful ' 
leaf  is  presented  at  intervals  of  one  and  a  half  minutes,  the 
caterpillar  tries  it  every  time  and  takes  about  the  same 
number  of  tentative  bites.  But  if  the  leaf  be  presented  at 
intervals  of  about  thirty  seconds,  the  caterpillar  takes  fewer 
and  fewer  bites,  and  then  refuses.  But  it  cannot  remember 
for  a  minute  and  a  half. 

The  limitations  of  instincts  are  very  interesting,  especially 
in  showing  how  different  instinctive  behaviour  is  from 
intelligent  behaviour,  but  it  must  be  emphasized  that  it  is 
part  of  the  conception  of  an  instinct  that  it  shall  be  service- 
able from  the  start.  To  a  greater  or  less  extent  it  must  be 
serviceable  for  survival  in  the  widest  sense,  and  serviceable 
also  '  as  affording  the  congenital  foundations  for  an  im- 
proved superstructure  of  behaviour  '.  Even  though  it  is  far 
from  perfect,  even  though  it  is  afterwards  greatly  improved, 
even  though  it  is  only  a  play  instinct  (which  is  far 


THE  WAYS   OF   LIFE  229 

from  being  a  mere  luxury) — an  instinct  is  always  service- 
able. 

That  animals  are  sometimes  led  astray  by  '  following 
their  instincts ',  is  well  known ;  the  birds  who  act  as  a 
cuckoo's  foster-parents  illustrate  this.  That  the  hereditary 
endowment  is  often  insufficient  for  every  emergency,  is 
also  well  known  ;  thus  cattle  will  sometimes  eat  poisonous 
herbs.  But  there  is  no  difficulty  here,  since,  on  the  whole, 
creatures  are  well  served  by  their  instincts.  It  is  impos- 
sible that  all  instincts  should  be  perfect  in  animals  whose 
environment  is  changeful  or  who  change  their  environment. 

The  Norwegian  lemmings,  when  they  form  migratory 
bands,  often  head  westwards,  and  continue  on  their  way 
with  great  persistence  and  considerable  pugnacity.  They 
swim  across  lakes,  but  are  apt  to  lose  their  bearings  in  the 
water  and  drown.  As  they  march,  their  ranks  are  thinned 
by  birds  of  prey  and  small  carnivores ;  even  the  reindeer 
trample  them  underfoot.  It  is  often  but  a  small  percentage 
that  reach  the  shores  of  the  North  Sea — a  select  band  of 
survivors  deserving  a  better  fate.  For,  true  to  their  instinct 
to  go  on,  they  swim  into  the  sea  and  are  drowned.  In  a 
case  vouched  for  by  Collett,  a  vessel  sailed  for  fifteen 
minutes  through  a  swarm,  the  water  being  alive  with 
them  as  far  as  the  eye  could  reach.  What  must  be  noted 
in  a  case  like  this,  is,  that  the  go-ahead  instinct  is  often 
serviceable,  though  it  cannot  avail  against  a  famine  or  the 
occurrence  of  seas  on  the  earth's  surface. 

The  instinct  to  go  on  is  very  strong  in  eels,  and  its  general 
effectiveness  is  manifest.  It  carries  them  over  difficulties 
and  unfavourable  conditions  if  these  are  not  too  long 
drawn  out.  It  can  hardly  be  urged  as  an  imperfection  that 
these  persistent  creatures,  both  as  elvers  and  afterwards, 


230  THE  WONDER  OF  LIFE 

work  their  way  into  fatal  culs-  de-sac.  Mr.  W.  L.  Bishop 
reports  that  in  the  water- works  of  Dartmouth,  Nova 
Scotia,  eels  caused  considerable  trouble  by  continually 
getting  into  the  water-mains,  and  blocking  the  service- 
pipes. 


SOME  DIFFICULT  PHENOMENA 

'  Feigning  Death '.  It  is  well  known  that  many 
Crustaceans  and  Insects  become  absolutely  motionless 
when  suddenly  disturbed.  There  they  lie,  without  moving 
a  feeler  or  a  limb,  as  if  they  were  dead.  This  may  be  very 
useful  when  they  are  being  hunted  by  enemies  who  only 
snap  at  moving  things,  who  perhaps  do  not  see  them 
unless  they  move.  The  phenomenon  is  very  familiar  and 
very  puzzling.  Whether  it  is  a  physiological  faint  or  an 
instinctive  feint,  who  can  tell  us.  But  it  is  admitted  by  all 
that  in  the  lower  animals  it  is  not  a  deliberate  '  playing 
'  possum  '  and  that  it  is  not  a  *  fear  paralysis  '. 

Bohn  deals  with  the  so-called  'feigning  death'  by 
pointing  out  that  it  comes  into  line  with  '  differential 
sensitiveness ',  which  is  exhibited  by  some  of  the  lower 
animals  in  face  of  a  sudden  change  in  the  environment. 
Single-celled  animals  and  tube- inhabiting  worms  show  it 
equally  well ;  they  retract  and  remain  quiet ;  the  duration 
of  their  passivity  varies  with  the  light  and  temperature ; 
after  several  experiences  in  succession  the  reaction  dwindles 
away.  There  is  a  strong  suggestion  here  of  the  so-called 
'  death- feigning  '  in  insects  and  crustaceans,  which  follows 
aD  sorts  of  stimuli,  which  varies  in  its  duration  with  the  tem- 
perature and  the  illumination,  which  wanes  after  it  has  been 
brought  on  repeatedly.  The  creature  passes  into  a  strange 


THE   WAYS   OF   LIFE 


231 


state  ;  one  limb  may  be  cut  off  after  another,  and  it  gives 
not  the  slightest  reaction.  As  Darwin  noted,  the  attitude 
is  often  not  at  all  like  the  death- attitude.  The  phenomenon 
may  be  exhibited  by  a  decapitated  insect.  There  seems 
reason,  then,  to  agree  with  Bohn  that  in  Crustaceans  and 
Insects  the  so-called  death- 
feigning  is  an  exaggeration  of 
the  '  differential  sensitiveness  ' 
of  simpler  animals. 

In  the  water-insect  known 
as  the  water- scori*  ion  (Rana- 
tra),  there  is  a  marked  '  death- 
feigning  ',  but  it  is  exhibited 
only  in  the  air,  which  the 
American  species,  at  any  rate, 
rarely  visits.  It  is  so  pro- 
nounced, both  in  young  and 
adult  forms,  that  the  creature 
can  be  cut  in  two  without 
any  response,  but  it  is  dim- 
cult  to  see  that  it  can  be  of 
any  value.  Mr.  S.  J.  Holmes 
writes  : — 


FIG.  43. — An  insect — Carassiua 
— standing  on  its  head 
in  the  '  cataleptic  '  or 
'  death-feigning '  state. 
A  little  less  than  natural 
size.  (After  Schmidt.) 


'  One  is  strongly  inclined  to 

believe  that  the  death-feint,  which  is  manifested  only 
when  the  insect  is  in  the  air,  is  rather  an  incidental 
result  of  certain  physiological  peculiarities  of  the  organism 
than  an  instinct  which  has  been  built  up  by  Natural 
Selection  for  the  benefit  of  the  species '. 

'Bluffing'. — Every  one  knows  how  the  cat  that  is 
chased  by  an  impudent  dog  suddenly  turns  and  'stands 


232  THE  WONDER  OF  LIFE 

at  bay ',  a  very  picture  of  wrath,  with  its  teeth  showing 
and  its  fur  all  on  end.  Some  have  supposed  that  the  cat 
makes  itself  look  bigger  and  that  the  dog  is  abashed  by 
the  sudden  change  of  dimensions.  But  the  idea  that  there 
is  deliberate  'bluffing'  cannot  be  considered,  even  with 
a  creature  as  clever  as  a  cat.  The  cat  is  angry,  and  some- 
times a  little  afraid;  the  raising  of  the  fur  is  a  reflex. 
What  makes  the  dog  slink  off  is  partly  the  abruptness  of 
the  change  of  tactics  and  partly  the  awareness  that  this 
little  spitfire  '  means  business  '. 

Now,  if  '  bluffing '  does  not  take  place  in  the  cat,  it  is 
still  less  likely  to  occur  among  the  lower  animals.  There- 
fore, when  we  observe  the  '  terrifying  attitude '  of  the 
puss-moth  caterpillar,  or  the  Eyed  Blenny  (Blennius 
ocellaris],  raising  and  waving  its  dorsal  fin  with  its  curious 
black  '  eye-mark '  when  it  is  attacked,  or  the  Russian 
tarantula  taking  a  pose  which  makes  it  look  biggest  and 
most  impressive,  we  must  not  too  hastily  conclude  that  the 
creatures  know  what  they  are  doing.  What  we  see  is 
probably  an  inherited  reflex,  and  is  probably  of  real 
utility  in  the  struggle  for  existence,  for  it  does  appear  to 
have  a  disconcerting  effect  on  enemies. 

'  Homing  '. — It  is  well  known  that  ants  can  find  their 
way  home  from  a  distance.  The  present-day  interpreta- 
tion does  not  postulate  any  special  'homing  instinct', 
but  regards  the  phenomenon  as  due  to  a  combination  of 
factors.  There  seems  no  doubt  that  use  may  be  made  of 
odoriferous  substances  left  on  the  track,  and  Bethe 
started  the  hypothesis  that  there  is  a  quantitative  or 
qualitative  difference  between  the  scent  on  the  way  from 
the  nest  and  that  on  the  way  to  the  nest. 

The  results  of  Turner's  experiments  (1907),  led  him  to 


THE  WAYS   OF  LIFE  233 

conclude  that  the  ants  learn  to  find  their  way.  They  make 
many  mistakes  at  first,  but  gradually  improve.  They 
associate  different  impressions  (olfactory,  tactile,  visual, 
etc.),  and  remember  certain  finger-posts.  According  to 
some,  there  is  a  '  muscular  memory '  of  the  movements 
effected  and  of  the  amount  of  work  done.  But  the  general 
view  is  that  the  homing  of  ants  is  the  result  of  the  practised 
combination  of  a  number  of  hints.  According  to  Pieron, 
the  way- finding  of  ants  is  most  frequently  due  to  the 
combination  of  diverse  sets  of  impressions.  These  are  often 
predominantly  visual,  as  in  Formica  fusca  and  F.  rufibarbis ; 
they  may  be  mainly  olfactory,  as  in  Lasius  flavus  and 
L.  fuliginosus  ;  in  the  very  blind  Aphcsnogaster  barbara 
they  are  mainly  muscular. 

The  homing  of  bees  and  digger-wasps  is  even  more 
striking  than  that  of  ants — so  striking  that  Fabre  felt 
compelled  to  postulate  a  capacity  more  subtle  than  ordinary 
memory,  '  une  sorte  d'intuition  des  lieux '.  He  caught 
ten  specimens  of  Cerceris,  marked  them,  put  them  in  a  box, 
took  them  three  kilometres  away,  and  liberated  them 
next  morning.  Of  the  ten,  five  returned  to  the  home. 
Some  specimens  of  Chalicodoma  were  taken  over  hill  and 
dale  to  a  distance  of  four  kilometres,  and  twenty  per  cent, 
returned.  Bethe  liberated  some  bees  in  the  middle  of 
Strasburg  and  others  at  the  same  distance  from  the  hive, 
but  in  the  country ;  those  from  the  streets  were  home  (in 
the  suburbs)  before  those  from  the  country.  Professor 
Yung,  of  Geneva,  made  a  very  interesting  experiment.  He 
took  twenty  bees  from  a  hive  near  the  lake,  put  them  in  a 
box,  and  took  them  six  kilometres  into  the  country,  where 
they  were  liberated.  Seventeen  returned,  some  in  an  hour. 
Next  day  the  seventeen  were  put  back  in  the  box  and 


234  THE  WONDER  OF  LIFE 

taken  on  a  boat  to  a  distance  of  three  kilometres  on  the 
lake.  When  liberated,  they  flew  off  in  all  directions,  but 
none  returned.  This  suggests  that  the  bees  build  up  a 
knowledge  of  the  country  round  about  them. 

Bouvier  concealed  the  entrance  to  the  nest  of  a  Bembex 
with  a  stone.  This  appeared  to  disturb  the  insect  a  little, 
but  it  lighted  on  the  stone.  When  the  stone  was  shifted, 
during  the  insect's  absence,  for  about  eight  inches,  the 
creature  returned  to  the  stone.  It  appeared  to  have  fixed 
the  stone  in  its  memory.  Further  experiments  go  to 
show  that  bees  and  similar  insects  serve  an  apprenticeship, 
that  they  have  a  remarkable  topographical  memory,  and 
that  they  begin  by,  so  to  speak,  feeling  their  way  from 
finger-post  to  finger-post.  The  Peckhams  speak  of  the 
'  systematic  study  of  the  surroundings,'  and  others  have 
described  the  trial  flight  of  bees  when  they  first  leave  the 
hive.  Buttel-Reepen  has  shown  that  bees  removed  from  the 
hive  before  they  have  had  this  '  orientation  flight '  do  not 
return,  and  that  if  the  hive  be  taken  some  miles  off,  a  new 
apprenticeship  has  to  be  served. 

There  are  other  data,  however,  that  go  to  support 
Fabre's  assumption  of  an  '  intuition  des  lieux '.  Thus 
Gaston  Bonnier  observed  that  bees  returned  straight  to 
the  hive — making  a  bee-line,  in  fact — from  a  distance 
of  as  much  as  three  kilometres.  When  they  were  carried 
afield  in  a  box  and  then  liberated,  they  made  for  the  hive, 
which  was  quite  invisible  behind  a  wood.  When  their 
eyes  were  obscured  with  blackened  collodion,  they  still 
found  their  way,  which  shows  that  vision  is  not  necessary. 
The  removal  of  the  antennae,  which  bear  the  so-called 
olfactory  organs,  did  not  prevent  their  return.  These 
facts  support  the  view  that  bees  have  a  '  sense  of  direc- 


THE  WAYS  OF   LIFE  235 

tion ',  more  or  less  comparable  to  that  of  carrier  pigeons, 
and  located  In  the  cerebral  ganglia. 

The  Peckhams  made  some  fine  experiments  on  '  homing  ' 
in  social  wasps.  For  instance,  they  captured  a  number  of 
wasps  leaving  the  nest  in  the  morning,  and,  having  stopped 
up  the  nest,  took  them  to  some  distance  off.  The  first  lot 
was  liberated  a  furlong  out  on  a  lake  ;  the  second  in  a  barn 
with  a  window  at  each  end — one  towards,  the  other  away 
from  the  nest ;  the  third,  three  hundred  yards  away  in 
the  country.  From  fifty  to  seventy  per  cent,  returned  to 
the  nest.  It  seemed  to  the  observers  that  the  wasps  rose 
high  in  the  air  and  flew  about  in  circles  until  they  saw 
something  they  remembered. 

Some  careful  observations  have  been  made  on  the 
'  homing '  habit  in  limpets.  In  many  cases,  it  has  been 
shown  that  particular  limpets  have  particular  sites  on  the 
rock,  and  that  they  return  to  these  after  they  have  been 
on  a  short  excursion.  They  appear  to  have  a  topographical 
memory,  which  fixes  impressions  not  only  of  the  particular 
site  but  of  its  surroundings.  The  reason  why  it  matters 
that  the  limpet  should  '  go  home ',  is  that  the  margin  of 
their  shell  grows  so  as  to  fit  the  little  inequalities  on  the 
surface  of  the  rock,  and  a  small  amount  of  water  is  thus 
retained  during  the  period  when  they  are  left  dry  by  the 
retreating  tide.  Lloyd  Morgan  found  that  of  twenty-one 
limpets  moved  for  eighteen  inches,  eighteen  found  their 
way  back ;  of  thirty-six  moved  for  twenty-four  inches, 
only  five  got  home  again. 

'Masking'. — Various  crabs,  such  as  the  common 
Hyas  araneus,  fasten  seaweed  on  to  their  carapace,  and 
thus  cover  themselves  with  effective  disguise.  When  they 
put  on  an  inconveniently  large  piece,  they  take  it  off  again 


236  THE  WONDER   OF  LIFE 

and  trim  it.  Some  crabs  use  the  tests  of  sea-squirts  or 
pieces  of  sponge  and  zoophyte.  In  a  number  of  higher 
crustaceans  (crabs,  lobsters,  etc.),  a  salivated  cement  of 
sand  is  plastered  over  the  carapace,  making  it  very  like 
the  substratum.  In  species  of  the  somewhat  primitive 
type  known  as  Dorippe,  the  posterior  limbs  are  turned 
upwards  and  they  hold  the  disguise — which  may  be  almost 
anything,  even  a  piece  of  glass — in  position  over  the  back. 
Most  remarkable  are  the  cases  where  crabs  take  seaweed 
of  the  colour  that  suits  their  usual  background. 

The  process  of  masking  in  one  of  the  spider-crabs  (Maja) 
has  been  very  carefully  studied  by  Minkiewiez.  The  crab 
seizes  a  piece  of  seaweed  in  its  forceps,  puts  it  into  its 
mouth  and  cuts  off  a  piece,  and  then  fixes  this  by  means  of 
its  forceps  on  the  back  or  on  the  walking  legs.  It  moves  the 
forceps  backwards  and  forwards  till  the  alga  fixes  on  some 
of  the  recurved  and  barbed  hooks  borne  on  the  carapace 
or  legs.  The  same  is  done  with  sponge,  hydroid  and  com- 
pound Ascidian,  and  Minkiewiez  got  his  crabs  to  dress 
themselves  up  in  pieces  of  silk  paper.  Professor  Fol 
once  made  a  similar  experiment,  giving  the  crab  pieces  of 
hay  and  white  paper  and  depriving  them  of  seaweeds. 
Unsatisfactory  as  the  dress  material  was,  it  was  duly 
utilized. 

Minkiewiez  made  the  interesting  experiment  of  placing 
two  or  three  thoroughly  cleaned  crabs  in  an  aquarium 
and  giving  them  pieces  of  silk  paper  of  two  colours — 
one  the  same  as  the  environment  and  the  other  different, 
with  the  result  that  the  crabs  chose  the  pieces  with  the  same 
colour  as  the  surroundings.  *  If  the  walls  are  white,  they 
will  be  covered  with  white  only;  they  will  take  neither 
green,  nor  yellow,  nor  black ;  if  the  walls  are  green,  they 


THE  WAYS   OF  LIFE  237 

will  be  clothed  in  green '.  In  an  aquarium  divided  into  two 
with  different  colours  (red  and  green),  he  placed  crabs 
which  had  in  a  preparatory  aquarium  clothed  themselves 
with  red  and  green.  The  red  crabs  went  towards  the  red 
end,  the  green  crabs  towards  the  green  end.  In  an  aquarium 
divided  into  three  equal  parts,  the  middle  one  white,  the 
other  two  black,  the  white  crabs  went  to  the  white  part 
and  remained  there.  In  a  control  experiment  in  another 
aquarium,  with  black  in  the  middle  and  white  on  both  sides, 
the  black  crabs  went  for  the  black. 

That  the  facts  are  suggestive  of  active  masking  and  of 
deliberate  choice  must  be  granted,  but  Minkiewiez  pointed 
out  the  danger  of  hurrying  to  a  generous  conclusion.  He 
refers  to  Fol's  observation  that  crabs  could  be  got  to  put 
on  a  dress  of  white  paper,  which  made  them  more,  not  less, 
conspicuous.  He  points  out  that  clothed  crabs  transferred 
to  an  aquarium  of  a  very  discordant  colour  make  no 
attempt  to  remove  their  old  costume,  though  they  hang 
on  new  papers  beside  the  old  ones.  Furthermore,  he  found 
that  crabs  put  into  a  black  aquarium  never  took  black 
paper  if  they  could  find  any  other  colour.  '  They  cover 
themselves  with  green,  red,  or  white,  making  a  bright 
patch  on  the  black  floor  of  the  aquarium,  instead  of  con- 
cealing themselves  '.  The  apparent  contradiction  between 
these  exceptional  facts  and  those  which  suggest  deliberate 
self-disguise  is  very  striking,  and  it  led  Minkiewiez  to 
inquire  carefully  into  its  significance. 

He  found  that  blinded  crabs  disguised  themselves  at 
once,  though  without  any  reference  to  the  colour  of  the 
surroundings.  Whenever  their  claws  touch  suitable  things 
the  routine  of  reflex  movements  begins,  their  mouth- 
appendages  are  next  touched,  and  then  the  dorsal  hooks. 


238  THE  WONDER  OF  LIFE 

The  brain  is  not  required  at  all,  which  corroborates  the 
observation  of  Bethe,  that  a  crab  in  which  the  connexion 
between  the  brain  and  the  ventral  nerve  cord  has  been  cut, 
can  walk  and  select  its  food  and  take  its  meals,  and  defend 
itself  very  much  as  usual.  So,  after  the  complete  severance 
of  the  brain,  one  of  Minkiewiez's  spider-crabs  was  often 
seen  to  disguise  itself,  executing  the  whole  series  of  move- 
ments in  the  proper  order. 

The  power  of  discriminating  between  different  rays  of 
light  is  well  seen  in  many  animals.  Minkiewiez  has  shown 
that  the  newly- hatched  larvae  (Zoaeee)  of  the  spider-crab 
(Maja  squinado)  are  strongly  attracted  to  the  light,  and 
under  a  spectrum  make  for  the  rays  of  the  shortest  wave- 
length— the  violet  and  blue.  The  red  Nemertean  worm, 
Linens  ruber,  is  negative  with  respect  to  diffused  light, 
but  when  it  is  illumined  by  coloured  light  it  makes  for 
red  and  yellow  rays  and  is  repelled  by  the  blue  and  green. 
In  diffused  light  in  an  aquarium  with  a  floor  of  two  colours 
(say  red  and  violet),  it  comes  to  rest  on  the  red  and  avoids 
the  violet.  If  the  colour  be  other  than  red  and  violet,  it 
always  seeks  out  the  background  nearest  red. 

Hermit-crabs  seem  to  be  very  suitable  animals  for  experi- 
mentation, as  they  do  not  get  excited  and  can  be  shifted 
about  and  placed  here  and  there  in  an  aquarium  while 
within  the  shelter  of  their  shell.  They  show  a  strong 
preference  for  a  white  background,  and  next  to  that  for 
a  green  one.  Apart  from  green,  the  attractive  value  of  a 
colour  corresponds  to  its  position  in  the  solar  spectrum. 
In  an  aquarium  with  a  floor  half  green,  and  half  any  other 
colour  but  white,  the  hermit  crabs  make  for  the  green 
side  whenever  they  get  their  eyes  out  of  their  sheltering 
shell,  and  Minkiewiez  found  that  during  the  day  they  never 


THE  WAYS   OF   LIFE  239 

crossed  the  boundary  line !  The  same  applies  to  an 
aquarium  half  white,  half  black.  The  order  of  their  prefer- 
ences is  thus  : — 

—Black  ->  red  ->  yellow  -*•  blue  ->  violet  ->  green  ->  white  + 

The  next  result  reached  by  Minkiewiez  was  very  remark- 
able, that  a  change  in  the  nature  of  the  medium  brings 
about  a  reversion  of  the  attractions  to  the  various  rays. 
When  distilled  water  was  added  to  the  sea  water  (25-80 
cubic  centimetres  to  100  cubic  centimetres),  the  Nemertean 
worm,  Linens  ruber,  turned  towards  the  most  refrangible 
rays  of  the  spectrum  as  decidedly  as  it  had  previously 
avoided  them  !  The  change  in  the  medium  disturbed  the 
physiological  condition  of  the  animal,  but  on  the  fourth 
day  the  original  attractions  manifested  themselves  again. 
When  a  worm  which  had  got  accustomed  to  the  diluted 
water  and  showed  its  normal  preference  for  red  was  put  back 
again,  after  two  or  three  weeks,  into  ordinary  sea  water, 
it  Avas  again  disturbed,  and  made  for  the  violet. 

Hermit-crabs  left  in  a  basin  without  change  of  water 
become  gradually  intoxicated  with  their  own  waste  pro- 
ducts, and  all  their  preferences  are  inverted.  The  scale 
of  values  remains  in  the  same  sequence,  but  the  direction 
of  movement  has  changed  to  the  opposite,  as  in  the  follow- 
ing line  : — 
+  Black  <-  red  •<-  yellow  •<-  blue  <-  violet  <-  green  <-  white  — 

Professors  Keeble  and  Gamble  have  shown  that  young 
prawns  (Hippolyte  varians),  almost  colourless  to  start 
with,  rapidly  assume  the  coloration  of  the  seaweed  on 
which  they  are  placed.  What  is  more,  the  adults  that  have 
put  on  some  definite  colour,  are  able  to  change  this  and 
assume  a  new  one  in  harmony  with  a  new  environment. 
Minkiewiez  got  similar  results  :  any  colour  can  be  changed 


24o  THE  WONDER  OF  LIFE 

into  any  other,  though  some  prawns  are  more  susceptible 
than  others.  '  Once  changed,  the  colour  of  the  Hippolyte, 
even  in  the  most  obstinate,  becomes  plastic,  and  can  be 
changed  with  astonishing  rapidity,  sometimes  in  ten 
minutes '. 

According  to  Minkiewiez,  what  it  seems  to  come  to  is 
this.  In  a  green  environment,  the  spider-crab  becomes 
positively  susceptible  to  green,  and  negative  in  relation 
to  other  colours.  It  will  disguise  itself  in  such  green  as  it 
can  find  growing  on  the  green  surfaces.  It  does  not  choose 
its  disguise.  When  it  is  transferred  to  an  aquarium  half 
red  and  half  green,  it  goes  to  the  green  half,  not  because  its 
disguise  is  green,  but  because  it  is  itself  attracted  by  green. 
It  does  not  choose  its  environment.  In  a  dark  aquarium 
the  crab  may  make  itself  conspicuous  by  putting  on  pieces 
of  light-coloured  paper  instead  of  black  paper,  for  any 
colour  is  more  attractive  than  black,  which  has  no  influence 
at  all. 

The  behaviour  of  the  spider-crab  in  its  self -concealment 
is  composed  of  two  parts.  In  the  first  place,  it  is  drawn  or 
driven  towards  certain  coloured  surfaces,  according  to  the 
sum  of  the  given  conditions.  Once  there,  and  in  touch 
with  material— usually  seaweed — it  begins,  in  the  second 
place,  to  cover  itself,  one  set  of  tactile  impressions  provoking 
certain  movements  of  the  claws,  which  lead  to  tactile  impres- 
sions of  the  mouth  parts  and  further  movements — and  so 
on,  until  the  whole  routine  is  accomplished.  We  have 
given  this  case  in  some  detail  because  it  illustrates  the  work 
of  the  modern  school,  who  rightly  believe  in  pushing  physio- 
logical interpretations  as  far  as  they  will  go  before  invoking 
an '  efficient  consciousness  '  or  the  like. 

In  Summary. — As  regards  the  theory  of  instinct,  there 


THE  WAYS   OF   LIFE  241 

are  three  main  views :  (a)  Instinctive  actions  are  re- 
garded by  some  as  concatenated  reflexes,  as  non- cognitive 
hereditary  dispositions  to  follow  a  certain  routine  Avhen  the 
trigger  is  pulled.  (6)  Instinctive  actions  are  regarded  by 
some  as  quite  inseparable  from  intelligence,  (c)  Instinct  and 
intelligence  are  regarded  by  Bergson  and  others  as  two 
radically  different,  though  complementary,  kinds  of 
knowing,  which  have  evolved  along  divergent  lines.  It  is 
too  soon  to  come  to  a  decision  in  regard  to  these  rival 
theories.  The  fact  remains  that  there  is  a  big  area  of 
animal  behaviour  of  a  peculiarly  fascinating  type  which  is 
conveniently  called  instinctive. 


INTELLIGENT  BEHAVIOUR 

When  we  pass  from  the  Invertebrates  to  the  Vertebrates, 
we  find  ourselves  in  a  new  atmosphere.  Instinct  begins 
to  count  for  less  and  intelligence  for  more.  There  are, 
indeed,  many  illustrations  of  intelligence  among  Inverte- 
brates and  of  instinct  among  Vertebrates,  but  on  the  whole 
the  big-brained  type,  which  reaches  its  climax  in  Birds 
and  Mammals,  is  one  which  is  relatively  poor  in  ready- 
made  predispositions  to  certain  lines  of  behaviour  and 
relatively  rich  in  its  power  of  learning  by  experience.  As 
Sir  Ray  Lankester  has  said,  the  big  brain  type  is  eminently 
educable. 

After  naturalists  condescended  to  credit  animals  with 
intelligence  analogous  to  their  own,  and  ceased  to  bundle 
all  animal  behaviour  together  and  label  it  '  instinctive  ', 
there  was  a  generous  reaction.  It  was  the  fashion  to  see  a 
Brer  Rabbit  everywhere,  and  to  read  the  man  into  the 
beast  without  let  or  hindrance.  All  sorts  of  delightful 


242  THE  WONDER  OF  LIFE 

anecdotes  of  animal  sagacity  were  collected  with  more 
zeal  than  discretion. 

We  may  associate  with  the  name  of  Romanes  in  particu- 
lar the  beginning  of  a  more  critical  period.  Though  he  was 
not  always  sufficiently  stern  himself,  he  did  important 
work  in  sifting  the  data,  and  in  trying  to  separate  out 
precise  observation  from  the  more  or  less  unconscious 
inferences  with  which  the  recorder  so  often  interpenetrates 
it.  He  drew  the  useful  distinction  between  perceptual 
inference  (intelligence),  where  a  conclusion  is  drawn  from 
concrete  representations,  and  conceptual  inference  (reason), 
where  the  syllogism  involves  general  concepts  ;  and  showed 
that  there  was  no  evidence  compelling  us  to  credit  animals 
with  more  than  the  former.  Considerable  progress  has 
also  rewarded  the  work  of  the  experimental  school,  who 
have  studied  the  process  of  '  learning  ',  of  forming  associa- 
tions, of  profiting  by  experience,  of  experimenting  in  novel 
situations,  and  so  on. 

Association. — It  was  a  great  step  in  evolution  when 
animals  began  to  associate  sensations  together.  We  mean 
by  a  sensation,  physiologically,  an  impression  made  on  the 
nervous  system  by  external  stimulus,  and  psychologically, 
an  awareness  (to  some  degree)  of  the  external  stimulus. 
Let  us  refer  briefly  to  some  of  the  experimental  work  which 
has  been  done  in  the  study  of  the  association  of  sensations. 
There  is,  for  instance,  the  work  of  Pavlov  and  his  school 
on  the  establishment  of  associations  in  the  dog.  It  is  well 
known  that  a  dog's  mouth  may  water  when  it  sees  food ; 
there  is  a  reflex  stimulation  of  the  salivary  glands,  not 
by  direct  contact  with  food,  but  circuitously  by  a  visual 
impression.  When  the  food  is  put  in  the  dog's  mouth, 
the  salivation  must  follow ;  when  the  stimulation  is  cir- 


FIG.  44.— Bird-catching    spider    (Mygale    avicularia)    catching    a 
humming-bird.     From  a  specimen. 


242 

anecdot 
zeal  tha 
We  m 
lar  the 
not   . 


THE   WONDER  OF  LIFE 

aa***fei  sagacity  were  collected  with  more 
r 

tii  the  name  of  Romanes  in  particu- 

»nore critical  period.     Though  he  was 

•'•>.•  stern  himself,  .  he  did  important 

«.=    ?•**<  »Ut&,  and  in  trying  to  separate  out 

-A**;-.^   ffron  the  more  or  less  unconscious 

-.   !.•(.»•»  l-h*  recorder  so  often  interpenetrates 

n**fn\  distinction  between  perceptual 

where  a  conclusion  is  drawn  from 

and  conceptual  inference  (reason), 

n-*e  general  concepts  ;  and  showed 

••IT  us  to  credit  animals^ 


U,t  5,-.s  n  ' 
has  been 
There  is, 
on  the  esr.  • 
known  that  &   • 
there  is  a  refl. 
by  direct  OOUM 
impression.     When 
the 


lution  when 

We  mean 

ir.ade  on  the 

psychologically, 

xternal  stimulus. 

.  •  •:  :  'Otimental  work  which 

xaation  of  sensations. 

Pavlov  and  his  school 

in  the  dog.     It  is  well 

•  ter  when  it  sees  food  ; 

•'    the  salivary  glands,  not 

«cuitously  by  a  visual 

-  in  the  dog's  mouth, 

-he  stimulation  is  cir- 


! 


THE  WAYS   OF  LIFE  243 

cuitous  the  result  is  inconstant.  Pavlov  showed  that  if 
a  whistle  is  always  sounded  when  a  dog  gets  something 
to  eat,  then  by  and  by  the  sound  of  the  whistle  will  make 
the  dog  salivate.  An  association  between  the  sound  and 
the  gustatory  excitation  has  been  established. 

The  stimulus  that  '  suggests '  the  salivation  may  be 
almost  anything  if  the  dog  has  the  association  estab- 
lished— it  may  be,  besides  sight  and  sound,  an  odour,  a 
movement,  a  change  of  temperature  or  illumination,  a 
scratching  of  the  skin,  and  so  on.  The  method  is  useful 
in  definitely  proving  the  animal's  sensitiveness  to  various 
stimuli — some  of  them  well  known  to  all  who  know  dogs, 
and  others  a  little  surprising — but  its  chief  value  is  in 
showing  the  establishment  of  cerebral  associations,  and  in 
discovering  their  laws.  The  experiments  leave  in  the  mind 
a  vivid  impression  of  the  remarkable  plasticity  of  the  dog's 
brain  in  forming  associations.  Thus,  Orbeli  succeeded  in 
establishing  a  reflex  between  the  salivation  and  the  shape 
of  the  letter  T  (as  distinguished  from  other  shapes)  thrown 
on  a  screen. 

Bohn  gives  some  other  instructive  illustrations.  Many 
fishes  show  no  sign  of  hearing  sounds,  and  yet  they  some- 
times hear  them.  For  Meyer  taught  some  fishes  in  a  couple 
of  months  that  whenever  a  certain  sound  was  made  they 
would  find  some  food  in  a  dark  chamber  in  their  aquarium. 
They  acquired  an  interest  in  the  sound  and  they  came 
gradually  to  associate  it  with  their  memory  of  food. 

There  is  a  special  interest  in  experiments  with  fishes, 
since  their  brain,  especially  in  bony  fishes,  or  Teleosts,  has 
stopped  at  a  low  level.  Some  observers,  like  Edinger,  deny 
them  even  memory.  M.  Oxner  has  recently  made  some 
instructive  observations  at  the  Oceanographical  Museum 


244  THE  WONDER  OF  LIFE 

at  Monaco  with  a  fish  called  Coris  julis,  whose  intelligence 
is  at  an  interesting  incipient  stage.  To  begin  with,  he 
showed  that  when  he  disguised  the  hook  very  cleverly,  he 
could  catch  the  same  fish  as  often  as  he  pleased.  But  this 
only  proved  that  the  disguising  of  the  hook  was  practically 
perfect,  and  that  the  fish  was  appetized.  If  there  was 
no  hint  of  the  hook,  there  was  nothing  which  an  unreflecting 
creature  could  learn.  A  certain  sensory  impression  raised 
a  recollection  of  a  pleasant  experience,  and  action  followed 
almost  like  a  reflex. 

Oxner's  experiments  with  the  sea-perch  (Serranus  scriba) 
are  very  instructive.  In  an  aquarium  he  hung  a  red  and 
a  green  cylinder  by  silk  threads  of  a  similar  colour,  and 
put  food  in  the  red  one  only.  For  the  first  two  days  the 
wary  fish  did  not  approach  the  cylinders  at  all.  On  the 
third  day,  after  fifteen  minutes'  '  deliberation ',  it  entered 
the  cylinder  and  ate  the  food ;  on  the  fourth  day  it  did 
this  after  five  minutes  ;  on  the  fifth  day  after  half  a  minute  ; 
from  the  sixth  to  the  tenth  day  it  rushed  in  at  once.  On 
the  eleventh  day  it  entered  a  fresh  red  cylinder  that  had 
no  food  in  it,  and  waited  there  for  three  minutes.  So  that 
one  may  reasonably  conclude  that  an  association  had  been 
established  between  the  red  colour  and  the  food. 

On  each  of  the  succeeding  six  days  the  fish  rushed  into 
the  empty  red  cylinder,  and  when  Oxner  dropped  in  some 
food,  a  little  was  taken.  On  the  eighteenth,  nineteenth  and 
twentieth  days,  the  fish  was  unappetized  and  would  not 
eat  the  food.  But  the  interesting  fact  was,  that  even  in 
the  absence  of  appetite,  the  fish  seemed  unable  to  resist 
rushing  into  the  red  cylinder.  The  association  worked 
almost  like  a  reflex.  It  may  be  noted  that  there  is  no 
particular  attraction  in  the  red  colour,  for  the  same  general 


THE  WAYS  OF  LIFE  245 

results  were  obtained  when  the  food  was  put  in  a  cylinder 
of  another  colour. 

Bouvier  was  able  to  prove  that  wasps  of  the  genus  Bembex 
associated  a  certain  stone,  for  instance,  with  the  way  to 
their  burrow.  It  has  been  shown  that  the  American 
crawfish,  the  crab,  and  the  hermit-crab  can  be  taught  to 
take  the  more  advantageous  or  the  easier  of  two  alternative 
paths.  Anna  Drzewina  gave  hermit-crabs  which  had  been 
deprived  of  their  shells  a  number  of  top-shells  (Trochus) 
with  the  openings  closed.  The  hermit-crabs  spent  futile 
days  and  nights  trying  to  use  the  closed  shells,  but  after 
six  to  eight  days  gave  it  up.  Even  when  a  shell  with  a 
paper  lid  was  given  them,  they  would  not  so  much  as  try. 
They  associated  the  form  of  the  shell  with  failure.  But 
when  other  closed  shells  of  a  different  shape  were  given  to 
them,  they  began  eagerly  again  their  futile  attempts  to 
win  a  way  in. 

Trial  and  Error. — In  illustration  of  another  experi- 
mental method,  we  may  refer  to  Professor  Thorndike's 
investigation  of  the  learning  powers  of  cats  and  dogs. 
He  contrived  cages  with  doors  which  could  be  opened  by 
the  manipulation  of  more  or  less  intricate  combinations  of 
bolts  and  levers.  Hungry  cats  and  dogs  were  shut  in 
and  were  tempted,  by  food  placed  just  outside,  to  solve 
the  problem  of  their  prison-doors.  In  similar  circumstances, 
we  should  probably  do  a  little  thinking,  make  one  trial, 
and  be  free.  But  this  was  not  what  the  cats  and  dogs  did. 
They  got  out  by  the  '  trial  and  error '  method ;  that  is  to 
say,  they  made  one  experiment  after  another  until  they 
hit  upon  the  fit  and  proper  way  of  working  the  mechanism. 

The  experiment  was  repeated  over  and  over  again,  and 
the  curves  recording  the  times  taken  to  escape  showed  a 


246  THE  WONDER  OF  LIFE 

gradual  descent.  If  the  animals  had  ideas  on  the  subject, 
they  did  not  seem  to  use  them.  They  learned  by  '  trial 
and  error,'  as  we  often  do  ourselves.  But  Professor  Thorn- 
dike  made  an  important  step  in  suggesting  that  the  pleasure 
of  the  meal  that  rewarded  escape  served  to  '  stamp 
in '  the  immediately  antecedent  association  between  the 
picture  of  the  interior  of  the  cage  and  the  successful  impulse 
that  led  to  the  succession  of  muscular  movements  effecting 
release.  This  is  Professor  Thorndike's  '  sense-impulse ' 
theory  of  learning. 

When  Thorndike's  cats  were  shut  up  in  boxes  which 
could  be  easily  opened  in  a  particular  way,  they  seemed 
to  get  out  by  accident.  On  subsequent  occasions  they 
did  not  take  quite  so  long,  and  they  gradually  learned  the 
trick.  Dogs  were  quicker,  and  monkeys  quicker  still. 
In  most  cases  the  method  seems  to  be  the  same — a  chance 
discovery,  and  subsequently  a  gradual  elimination  of  the 
ineffective  attempts.  But  there  appear  to  be  some  cases 
where  it  looks  as  if  the  animal  had  an  intuition  of  the  line 
of  effective  trial,  as  if  it  '  had  a  notion '  of  the  best  thing 
to  do. 

Experiments,  especially  in  getting  out  of  labyrinths,  have 
been  made  with  rats  and  guinea-pigs,  chickens  and  sparrows, 
and  some  other  creatures.  The  story  is  in  most  cases 
essentially  the  same.  The  animals  learn  more  or  less 
quickly  to  profit  by  their  mistakes  and  to  conquer  the 
difficulties  of  the  situation.  In  some  cases  (Watson's 
white  rats)  the  learning  appears  to  depend  in  great  part  on 
a  muscular  memory  of  the  effective  sequence  of  movements, 
for  the  elimination  of  sight,  hearing  and  smell  and  a  good 
deal  of  tactility  did  not  seem  to  make  much  difference 
to  the  education  in  the  maze. 


THE   WAYS   OF  LIFE  247 

Of  great  interest  are  the  experiments  made  by  Yerkes 
on  '  dancing  mice  '.  These  fascinating  creatures  represent 
a  peculiar  variety,  of  unknown  origin,  which  has  been  the 
subject  of  artificial  selection.  They  are  characterized  by 
the  inability  to  move  far  in  a  straight  line  without  whirling 
or  circling  about  with  extreme  rapidity.  They  are  quite 
deaf,  except  sometimes  during  the  third  week  of  life. 
Their  power  of  discriminating  differences  in  brightness  is 
acute,  but  their  colour- vision,  in  the  strict  sense,  is  poor. 
They  are  quick  to  perceive  movements,  but  make  little 
of  form.  They  have  considerable  powers  of  learning  and 
can  remember  an  acquired  habit  for  2-8  weeks  after  disuse. 
What  has  been  forgotten  is  more  quickly  re-learned. 

Dr.  Yerkes  arranged  in  their  cage  two  passages,  with  doors 
which  bore  movable  cards  differing  in  colour  or  in  surface. 
One  passage  led  to  food,  the  other  to  a  slight  electric  shock. 
The  food  was  sometimes  to  the  right  and  sometimes  to  the 
left,  but  the  door  which  led  to  it  was  marked  with  the 
same  kind  of  card.  When  there  were  many  changes  the 
mice  hesitated  a  good  deal,  going  from  one  to  another 
and  touching  the  cards. 

This  point  is  of  great  interest,  and  must  be  emphasized. 
When  the  mouse  found  the  right-hand  door  to  be  the  path 
to  food  and  freedom  several  times  in  succession,  it  tried 
the  plan  of  keeping  to  that  door.  When  it  found  that 
the  cards  were  being  alternated,  it  learned  also  to  alternate. 
When  it  found  that  this  did  not  work — when  the  changes 
were  irregular — then  it  brought  all  its  powers  of  discrimina- 
tion to  bear  on  the  problem.  The  learning  how  to  '  choose  ' 
aright  was  quickest  when  the  difference  in  the  illumination 
of  the  two  cards  was  most  marked  (colour  in  itself  does 
not  seem  to  count),  and  it  was  also  noteworthy  that  when 


248  THE  WONDER  OF  LIFE 

fine  discrimination  was  necessary,  a  strong  electrical  stimu- 
lation— the  punishment  of  error — seemed  to  hinder,  not  to 
help,  progress. 

The  case  of  the  dancing  mouse,  so  carefully  studied 
by  Dr.  Yerkes,  seems  peculiarly  interesting  because  of 
what  one  may  call  its  nonchalance  and  inattentiveness. 

'  Most  Mammals  which  have  been  experimentally  studied 
have  proved  their  eagerness  and  ability  to  learn  the  shortest, 
quickest  and  simplest  route  to  the  food  without  the  addi- 
tional spur  of  punishment  for  wandering.  With  the  dancer 
it  is  different.  It  is  content  to  be  moving — whether  the 
movement  carries  it  directly  to  the  food-box  is  of  secondary 
importance.  On  its  way  to  the  food-box,  no  matter 
whether  the  box  be  slightly  or  strikingly  different  from 
its  companion  box,  the  dancer  may  go  by  way  of  the 
wrong  box,  may  take  a  few  turns,  cut  some  figure  eights, 
or  even  spin  like  a  top  for  a  few  seconds  almost  within 
vibrissa-reach  of  the  food-box,  and  all  this  though  it  be 
very  hungry '. 

But  in  spite  of  this  lack  of  concentration,  it  learns  to 
discriminate  successfully. 

It  is  difficult  to  know  how  much  imitation  counts  for  in 
animal  behaviour.  A  monkey  which  has  learned  to  work 
a  piece  of  mechanism  is  sometimes  able  to  teach  others  to 
imitate  all  the  required  movements,  but  often  it  meets 
with  the  variety  of  futile  imitations  that  other  teachers  are 
familiar  with.  In  one  case,  the  simple  trick  of  reaching  a 
fruit  with  a  stick  was  learned  by  one,  yet  never  imitated 
by  his  companions.  It  is  probable  that  in  the  natural 
life  of  the  creature,  and  in  the  play  period,  imitation  counts 
for  much  more  than  experiment  has  as  yet  indicated. 


THE  WAYS  OF  LIFE  249 

It  is  not  even  certain  that  a  cat  can  catch  a  mouse  without 
having  been  shown  the  way ! 

In  regard  to  instinctive,  as  well  as  intelligent  behaviour, 
it  is  probable  that  the  influence  of  others  counts  for  much 
— probably  for  more  than  is  generally  allowed.  Taken 
singly,  the  ant,  the  bee  or  the  termite  has  not  a  great  deal 
to  say  for  itself ;  but  '  the  co-operative  work  of  the  hive  or 
nest  is  amongst  the  greatest  wonders  of  nature  '.  '  This  ', 
says  Professor  Carveth  Read,  '  perhaps  may  be  best  ex- 
plained by  the  incessant  trying  of  all  the  operative  ants,  or 
bees,  or  termites,  at  their  several  tasks,  in  which  individuals 
often  fail,  but  have  their  work  made  good  by  the  trying  of 
others  '.  As  Turner  points  out  in  his  study  of  '  homing  ' 
in  ants,  the  appearance  of  concerted  division  of  labour 
may  be  deceptive,  they  supplement  one  another  because  all 
are  trying.  Thus,  flurried  ants  carrying  pupae  may  hide 
these  under  a  stone,  and  others  who  know  the  way  may 
rescue  the  pupae  if  they  discover  them. 

As  every  one  knows,  a  piece  of  behaviour  which  was 
*  thought  out '  to  begin  with,  or  required  intelligent  control 
at  every  turn,  may  be  repeated  so  often  that  the  brain 
is  modified  by  its  performance,  and  the  need  for  attention 
and  control  ceases.  In  a  word,  it  becomes  habitual.  '  A 
habit  is  a  more  or  less  definite  mode  of  procedure  or  kind 
of  behaviour  which  has  been  acquired  by  the  individual  and 
has  become,  so  to  speak,  stereotyped  through  repetition '. 


INSTINCT  AND  INTELLIGENCE 

When  a  newly-hatched  coot  or  blackheaded  gull  is 
tumbled  into  water,  it  swims  well — instinctively  ;  when  the 
hens  come  running  when  the  hen-wife  calls  '  Tuck- Tuck  ', 


250  THE   WONDER  OF  LIFE 

they  are  putting  two  and  two  together  in  a  simple  way. 
When  a  dog  turns  round  and  round  and  smooths  the  herb- 
age of  the  hearthrug  into  a  bed  for  the  night,  it  is  obeying 
an  ancient  instinct ;  when  it  tries  various  ways  of  getting  a 
stick  with  a  crooked  handle  through  a  fence  of  close-set 
uprights,  it  is  using  its  intelligence.  When  a  horse  shies 
at  an  unexplained  rustling  in  the  hedgerow,  it  does  so 
instinctively ;  when  it  takes  the  market-cart  safely  home 
with  the  driver  asleep,  it  does  so  intelligently.  When 
inexperienced  bees  deal  successfully  with  flowers,  the  per- 
formance is  instinctive ;  when  they  set  up  house  in  a  tree 
or  mend  a  broken  comb  in  an  economical  and  effective  way, 
intelligence  is  probably  at  work.  When  a  bird  utters  its 
call-note  before  it  is  hatched,  that  is  instinctive ;  when 
a  parrot  tells  its  mistress  that  it  is  dinner-time,  that  is 
more  or  less  intelligent. 

In  these  instances  we  have  contrasted,  in  a  simple  way, 
instinctive  and  intelligent  behaviour.  It  seems  clear 
that  whether  the  difference  between  them  be  of  degree  or 
of  kind,  there  is  a  difference  of  sufficient  importance  to 
warrant  the  use  of  two  different  words.  But  it  seems  neces- 
sary to  admit  that  it  is  not  easy  to  discover  either  kind  of 
behaviour  in  a  perfectly  pure  form.  Instinctive  behaviour 
has  often  a  spice  of  intelligence  along  with  it,  or  is  modified 
by  intelligent  '  learning '.  Intelligent  behaviour  often 
utilizes  instinctive  dispositions  as  a  basis. 

That  the  distinctive  call-note  of  a  bird  is  sometimes 
instinctive  is  satisfactorily  proved  by  cases  where  the 
characteristic  sound  is  uttered  before  the  young  bird 
is  hatched.  Mr.  Hudson  cites  the  case  of  a  young 
Rhynchotus  rufescens,  isolated  when  it  was  getting  out  of 
the  egg-shell  and  reared  beyond  reach  of  education,  which 


THE  WAYS  OF  LIFE  251 

was  nevertheless  accustomed,  long  before  it  was  full-grown, 
to  retire  to  a  dark  corner  of  the  room  and  give  forth  its 
characteristic  evening  song.  Young  coots  hatched  in  an 
incubator  utter  the  same  note  as  their  fellows  in  natural 
conditions. 

But  this  cannot  be  the  whole  story,  for  there  is  no  reason 
to  doubt  the  experiments  made  by  the  Hon.  Daines  Barring- 
ton,  one  of  Gilbert  White's  correspondents.  He  reared  linnets 
under  skylarks,  woodlarks,  and  titlarks,  and  found  that 
they  learned  the  song  of  their  foster- parent  in  each  case. 
This  points  to  the  conclusion  that  imitation  counts  for  a 
great  deal.  It  is  likely  that  many  young  birds  learn  their 
song  from  their  parents.  Mr.  Hudson  reports  that  in  the 
case  of  the  oven-bird  the  parents  sing  a  sort  of  duet  together, 
which  the  young  birds,  when  only  partially  fledged,  prac- 
tise inside  the  nest  in  the  intervals  when  the  parents  are 
absent.  Mr.  G.  W.  Bulman,  a  careful  observer,  gives  a  cir- 
cumstantial account  of  the  yellow-hammer's  singing  lessons. 
The  whole  subject  requires  more  attention  and,  above  all, 
some  careful  experimenting. 

The  intrusion  of  intelligence  upon  an  instinctive  routine 
is  probably  seen  when  a  bee  that  is  unable  to  get  at  the 
nectar  of  a  flower  in  the  ordinary  legitimate  manner, 
proceeds  to  cut  a  hole  through  the  base  of  the  tube.  Many 
years  ago  Hermann  Miiller  pointed  out  that  Bombus 
terrestris,  which  has  a  shorter  proboscis  than  some  other 
species  of  the  genus,  often  tries  in  vain  to  suck  the  flowers 
of  the  oxlip  (Primula  elatior),  and  that  it  does  not  seek  the 
short  cut  until  it  has  convinced  itself  by  experience  that 
the  other  method  will  not  work. 

In  many  cases,  however,  bees  which  could  suck  the  flower 
in  the  ordinary  way,  may  also  bite  a  hole  through.  Hermann 


252  THE    WONDER  OF  LIFE 

Miiller  found  that  this  practice  was  especially  common 
when  flowers  grow  in  masses  and  are  very  much  visited. 
Gnawing  the  hole  means  losing  time  in  the  first  instance, 
but  it  saves  much  time  afterwards.  The  bees  are  able  to 
discover  more  rapidly  what  blossoms  are  worth  anything. 
The  more  minutely  such  facts  are  inquired  into  the  more 
significant  they  become.  Thus  Professor  Francis  Darwin 
noted  in  regard  to  the  wood- vetch  (Lathyms  sylvestris) 
that  the  bee  bites  the  hole  just  at  the  best  place.  The 
honey  is  secreted  within  a  nectary  enclosed  by  the  united 
filaments  of  nine  stamens  ;  there  are  two  '  nectar-holes  '  at 
the  base ;  and  the  bees  gnaw  a  hole  exactly  over  the  left 
nectar-hole,  which  is  larger  than  the  right. 

'  It  is  difficult  to  say  how  the  bees  have  acquired  this 
habit.  Whether  they  have  discovered  the  inequality  in 
the  size  of  the  nectar-holes  in  sucking  the  flowers  in  the 
proper  way,  and  have  then  utilized  this  knowledge  in  deter- 
mining where  to  gnaw  the  hole ;  or  whether  they  have 
found  out  the  best  situation  by  biting  through  the  vexillum 
at  various  points,  and  have  afterwards  remembered  its 
situation  in  visiting  other  flowers.  But  in  either  case 
they  show  a  remarkable  power  of  making  use  of  what  they 
have  learned  by  experience '. 

In  other  words,  there  is  distinct  intrusion  of  intelligence 
into  the  domain  of  instinct. 

In  further  illustration  of  the  subtle  admixture  of  intelli- 
gence with  instinct,  one  of  Fritz  Miiller's  observations 
may  be  cited.  In  a  hive  of  Brazilian  stingless  bees  (Trigona 
mirim),  the  workers  had  completed  and  filled  forty-seven 
cells,  eight  on  a  nearly  finished  comb,  thirty-seven  on  the 
following,  and  four  around  the  first  cell  of  a  new  comb. 


THE  WAYS  OF  LIFE  253 

'  When  the  queen  had  laid  eggs  in  all  the  cells  of  the 
two  older  combs,  she  went  several  times  round  their  circum- 
ference (as  she  always  does,  in  order  to  ascertain  whether 
she  has  not  forgotten  any  cell),  and  then  prepared  to 
retreat  into  the  lower  part  of  the  breeding  room.  But 
as  she  had  overlooked  the  four  cells  of  the  new  comb,  the 
workers  ran  impatiently  from  this  part  to  the  queen,  pushing 
her,  in  an  odd  manner,  with  their  heads,  as  they  did  also 
other  workers  they  met  with.  In  consequence,  the  queen 
began  again  to  go  around  on  the  two  older  combs,  but 
as  she  did  not  find  any  cell  wanting  an  egg,  she  tried  to 
descend ;  but  everywhere  she  was  pushed  back  by  the 
workers.  This  contest  lasted  for  a  rather  long  while, 
till  at  last  the  queen  escaped  without  having  completed 
her  work.  Thus,  the  workers  knew  how  to  advise  the 
queen  that  something  was  as  yet  to  be  done,  but  they 
knew  not  how  to  show  her  where  it  had  to  be  done '. 

What  is  called  '  the  plasticity  of  instinct '  illustrates  the 
modifying  influence  of  intelligence.  One  of  Romanes's 
examples  may  be  cited.  He  took  three  orphaned  ferrets 
and  gave  them  to  a  young  Brahma  hen  which  was  sitting 
on  dummy  eggs.  She  had  never  reared  a  brood  of  chickens, 
so  she  was  quite  unprejudiced.  On  the  other  hand,  it  is 
interesting  to  note  that  she  had  been  nearly  killed  by  an  old 
ferret  a  few  months  before,  so  she  should  not  have  shown 
any  partiality  for  that  tribe.  As  a  matter  of  fact,  she  took 
to  them  immediately,  and  she  sat  on  them  for  rather  more 
than  a  fortnight,  nearly  up  to  the  time  when  their  eyes 
were  open.  The  ferrets  were  at  first  taken  from  the  nest 
to  be  fed  with  milk,  but  as  this  procedure  caused  the  foster- 
mother  much  uneasiness,  they  were  afterwards  fed  in  the 
nest — an  arrangement  with  which  the  hen  was  perfectly 
satisfied.  She  seemed  to  be  puzzled  at  the  lethargy  of  her 


254  THE  WONDER  OF  LIFE 

'  offspring ',  who  could  not,  of  course,  follow  her  when  she 
occasionally  flew  off  the  nest  and  summoned  them.  After 
one  day  she  was  quite  aware  of  the  meaning  of  the  ferrets' 
hoarse  cries,  so  different  from  a  chick's  piping  note,  and 
she  would  run  in  an  agitated  manner  to  any  near  place 
where  Mr.  Romanes  hid  them.  There  was  no  evidence, 
however,  of  a  reciprocal  understanding,  for  the  ferrets 
showed  no  responsiveness  to  the  hen's  clucking. 

During  the  whole  fortnight  the  hen  sat  almost  con- 
tinuously. 

'  She  used  to  comb  out  their  hair  with  her  bill,  in  the 
same  way  as  hens  in  general  comb  out  the  feathers  of  their 
chickens.  While  engaged  in  this  process,  however,  she 
used  frequently  to  stop  and  look  with  one  eye  at  the 
wriggling  nest-full  with  an  inquiring  gaze  expressive  of 
astonishment.  At  other  times,  also,  her  family  gave  her 
good  reason  to  be  surprised ;  for  she  used  often  to  fly  off 
the  nest  suddenly  with  a  loud  scream — an  action  which 
was  doubtless  due  to  the  unaccustomed  sensation  of  being 
nipped  by  the  young  ferrets  in  their  search  for  the  teats ' 

This  interesting  case  has  many  parallels,  and  the  series 
of  them  afford  astonishing  illustrations  of  the  plasticity 
of  instinct. 

EDUCATED  ANIMALS 

When  we  study  horses,  elephants,  dogs,  cats,  monkeys, 
and  other  '  clever '  Mammals,  it  seems  necessary  to  admit 
that  they  have  good  memories,  that  they  have  a  power  of 
rapidly  forming  associations,  that  they  profit  by  experience, 
that  they  can  adapt  old  means  to  new  ends,  that  they  can 
'  put  two  and  two  together '.  They  must  be  granted  the 
power  of  perceptual  inference,  and  there  are  some  facts  con- 


THE  WAYS   OF  LIFE  255 

nected  with  the  education  of  higher  animals  which  suggest 
that  we  have  swung  to  the  extreme  of  crediting  animals 
with  too  little  mental  capacity. 

Every  one  knows  that  much  can  be  achieved  by  the 
patient  training  and  persuasion  of  big-brained  higher 
animals,  such  as  those  which  we  have  named,  but  no 
one  yet  knows  how  much.  Elephants  make  very  clever 
workers  and  the  educability  of  army  horses  or  of  shepherds' 
dogs  is  astonishing.  When  the  late  Lord  Avebury  asked 
his  dog  Van  if  it  wanted  to  go  for  a  walk,  it  used  to  run  to 
its  box  of  printed  cards  and  fetch  the  one  with  OUT  on 
it.  It  would  bring  other  cards,  such  as  BONE  or  TEA,  when 
it  was  invited  to  enjoy  these  luxuries.  The  same  sort  of 
associative  power  was  even  more  developed  in  Dr.  Romanes's 
chimpanzee,  '  Sally ',  who  would  hand  you  three  straws, 
or  four  straws,  and  so  on,  as  you  asked  her.  To  save  time, 
she  used  sometimes  to  double  one  of  the  straws  and  present 
the  two  ends  between  her  fingers  and  thumb,  making 
three  straws  do  duty  for  four.  And  it  was  an  interesting 
fact  that  when  she  was  refused  a  reward  in  such  cases, 
she  used  to  straighten  out  the  bent  straw  and  make  the 
number  right  by  picking  up  another.  This  appreciation  of 
numbers  is  very  interesting,  but  it  is  mere  child's  play 
compared  with  the  arithmetical  powers  that  many  hard- 
headed  naturalists  have  recently  felt  compelled  to  recognize 
in  the  '  thinking  horses  '  of  Elberfeld. 

The  story  of  the  so-called  '  thinking  horses '  begins 
with  '  Clever  Hans ',  who  was  taught  by  Herr  Von  Osten 
to  give,  by  stamping,  the  answers  to  a  long  and  varied  list 
of  arithmetical  questions.  The  case  was  carefully  investi- 
gated in  the  Psychological  Laboratory  of  the  University  of 
Berlin,  and  the  general  verdict  was  that  the  horse  observed 


256  THE  WONDER  OF  LIFE 

its  questioner  very  attentively  and  took  note  of  ordinarily 
imperceptible  and  unconscious  movements  of  the  head  and 
body  which  indicated  when  he  should  stop  stamping.  It 
was  very  clever  of  the  horse  to  utilize  the  unconscious  signals, 
but  it  was  not  arithmetic.  Pfungst  declared  that  '  Clever 
Hans  '  could  not  read  figures  or  words,  as  was  alleged,  that 
he  could  not  spell,  or  count,  or  perform  arithmetical 
operations,  and  that  even  his  memory  was  poor.  It  only 
remained  to  say  that  he  was  a  very  well-meaning  and  an 
uncommonly  attentive  horse.  '  Clever  Hans  ',  rather  shorn 
of  his  glory,  passed  into  the  hands  of  Herr  Krall,  a  well-to-do 
merchant  in  Elberfeld,  who  took  precautions  (e.g.  by 
using  blinders)  to  keep  him  from  receiving  any  visual 
signals  during  the  experiments,  and  was  still  able  to  get 
correct  answers.  With  increasing  age,  however,  '  Hans  ' 
became  tired  of  '  arithmetic ',  and  would  obstinately 
refuse  to  do  any  more  of  whatever  it  was  that  he  had 
done.  Convinced  that  the  critics  were  missing  part 
of  the  truth,  Krall  started  afresh  with  two  young  Arab 
horses — Muhamed  and  Zarif — of  two  and  two  and  a  half 
years  respectively,  which  previous  experience  with  '  Hans ' 
enabled  him  to  train  in  a  more  effective  way. 

Krall  accustomed  his  horses  to  the  appearance  of  letters, 
figures,  words,  and  the  like,  which  were  hung  up  in  their 
*  schoolroom ' ;  he  taught  them  for  one  to  two  hours  a 
day  ;  he  carefully  avoided  routine ;  he  used  '  blinders  '  to 
eliminate  unconscious  visual  hints,  and  made  an  improved 
sounding-board  for  stamping  the  answers  on.  He  taught  his 
pupils  to  indicate  units  with  the  right  foot,  tens  with  the 
left,  hundreds  with  the  right,  so  that  126,  which  meant  126 
stamps  for  Hans,  involved  only  9  for  Muhamed  and  Zarif. 
'  Nothing  ',  '  no  ',  '  not '  and  '  none  '  were  indicated  by 


THE  WAYS   OF  LIFE  257 

one  movement  of  the  head  from  left  to  right.  Gently  and 
good-humouredly  he  taught  them  to  associate  a  certain 
sound  or  sight  with  a  certain  number,  a  certain  sound  or 
sight  with  a  certain  object,  or  even  operation.  His  educa- 
tion was  run  on  association  lines.  Very  gradually  he  got 
them,  he  thinks,  to  '  understand '  addition,  subtraction, 
multiplication  and  division.  In  the  course  of  time  they 
were  able  to  deal  with  fractions  and  to  extract  square 
roots  and  cube  roots.  Dr.  Hartmann,  of  Koln,  got  a  friend 
to  extract  three  cube  roots  and  put  the  questions  and 
answers  in  separate  envelopes.  In  the  stable  he  opened 
the  first  envelope  and  dictated,  '  Cube  root  of  13,824  '. 
In  a  few  seconds  came  the  answer,  24,  which  Hartmann 
confirmed  by  opening  the  relevant  envelope.  The  cube 
root  of  29,791  was  stated  to  be  31.  The  cube  root  of 
103,823  was  given  first  as  57  and  then,  rightly,  as  47. 

Professor  Buttell-Reepen  got  a  friend  to  put  a  number 
of  arithmetical  questions  in  separate  envelopes  and  the 
answers  in  others.  Neither  he  nor  Krall  knew  what  they 
were.  One  was  the  square  root  of  3,364,  and  \/  3,364  was 
written  on  the  board.  Muhamed  stamped  32  (wrong), 
44  (wrong),  then  twice  wrong,  and  then  58,  which  is  right. 

Professor  H.  von.  Buttel-Reepen  relates  a  very  interesting 
experience.  In  September  of  last  year  he  went  one  day, 
with  Professor  Ziegler,  to  KralPs  stables  half  an  hour  earlier 
than  had  been  arranged.  In  the  yard  they  fell  in  with  the 
Shetland  Pony  '  Hanschen  ',  and  resolved  to  make  some 
experiments  in  the  owner's  absence.  They  got  out  the 
blackboard  and  the  stamping-board,  and  without  a  word 

33 

Professor    Ziegler    wrote    down    the   sum    n.     Hanschen 

stood  waiting  before  the    stamping-board    and    at    once 

s 


258 


THE   WONDER  OF   LIFE 


rapped  out  the  correct  answer.  This  is  a  very  instructive 
instance.  The  pony  had  been  taught  at  intervals  for 
about  six  months  ;  it  had  never  been  previously  questioned 
in  the  yard,  nor  by  strangers.  A  short  distance  off  there 
was  a  groom  brushing  the  yard,  and  another,  Albert,  was 
brushing  Zarif,  but  they  took  no  part  in  the  proceedings  ; 
and  before  a  second  trial,  Albert  went  into  the  stable. 
Another  sum  was  written  on  the  board,  JJ,  and  the  words 
were  said,  '  Now,  Hanschen,  add  the  two  figures  and  you 
will  get  some  carrots  '.  The  right  answer,  which  chanced 
to  be  the  same  as  before,  was  at  once  rapped  out.  At 
this  stage  the  owner  and  teacher  appeared  on  the  scene, 
but  remained  at  a  distance  of  five  or  six  yards.  The  pony 
did  two  more  sums,  both  wrong  at  the  first  trial,  and  then 
right.  When  the  answer  is  wrong,  and  no  reward  or 
recognition  is  given,  the  pony  begins  to  paw  again,  some- 
times giving  the  right  answer,  sometimes  persisting  in 
the  wrong  one. 

Just  a  little  need  be  said  about  the  spelling  and  reading 
lessons,  which  were  not  nearly  so  striking.  A  board  was 
hung  up,  arranged  on  the  plan  indicated  below  : — 


1 

2 

3 

4      etc. 

3 

~ 

.0 

e 

n 

1 

20 

a 

h 

1 

30 

i 

d 

g 

w      etc. 

40 

etc. 

THE  WAYS   OF  LIFE  259 

Each  letter  is  denoted  by  two  figures,  units  in  the  upper 
horizontal  row  and  tens  in  the  left  vertical  row.  Thus 
e  is  represented  by  11,  which  involved  two  stamps — one 
stamp  with  the  right  foot  and  one  with  the  left ;  and  n  by 
12,  which  involved  two  stamps  with  the  right  foot  and 
one  with  the  left.  The  horses  insisted  on  spelling  phonet- 
ically and  in  omitting  the  vowels  ;  thus  '  Pferd '  was 
'  Ferd  '  and  '  Essen  '  was  '  S  N  '  to  them.  It  may  be  noted 
that  Krall  taught  the  alphabet  and  spelling  on  the  old- 
fashioned  lines.  Pointing  to  '  k ',  he  told  the  horses, 
'  this  is  ka  ' ;  pointing  to  '  p  ',  '  this  is  pe  '.  It  is  hardly 
surprising  that,  even  after  six  months'  learning,  the  horses 
were  very  shaky  about  the  spelling  of  a  word  like  brod 
(bread),  though  they  had  strong  practical  reasons  for 
making  sure  of  a  word  with  such  pleasant  associations. 

Let  us  note,  however,  one  of  the  spelling  tests.  Krall 
asked  Muhamed  if  he  wished  a  carrot,  and  got  the  usual 
emphatically  affirmative  nod.  '  Well ',  said  Krall,  '  pay 
close  attention ;  this  gentleman's  name  is  B-u-t-t-e-l 
(spelling  it),  spell  that '.  Muhamed  began  with  an  '  h  ', 
presumably  for  Herr,  being  a  well-bred  horse,  and  then 
wandered.  Krall  repeated  with  slow  emphasis,  Buttel, 
and  the  horse  answered,  '  bdul '.  To  the  question,  Where 
does  the  '  u  '  come  in  ?  Muhamed  answered  by  stamping 
twice.  '  Good  ',  said  Krall,  '  then  in  the  second  place  ',  and 
the  horse  answered,  '  budl '. 

The  verdict  of  several  competent  observers,  such  as 
Professors  H.  Kraemer,  P.  Sarasin,  H.  E.  Ziegler,  Claparede, 
Buttel-Reepen,  is  to  the  effect  that  the  horses  do  in  some 
measure  understand  what  they  are  being  trained  to 
do,  that  they  do  in  some  mysterious  way  calculate. 
Several  general  arguments  may  be  used  in  support  of 


260  THE  WONDER  OF  LIFE 

this  view.  (1)  The  horse  is  a  very  intelligent  creature  ;  it 
has  a  remarkably  fine  brain.  Perhaps  KralFs  pupils  are 
being  led  by  him  to  cultivate  fallow  areas  in  their 
unusually  rich  cerebral  estate.  (2)  The  analogy  of  calcu- 
lating boys  is  suggestive,  for  some  of  these  have  been  very 
backward  in  other  respects,  unable  to  read  or  write, 
unaware  of  conventional  methods  of  arithmetic,  and  so  on. 
Professor  von  Buttel-Reepen  cites  the  case  of  the  Italian 
peasant-boy  who  extracted  the  cube-root  of  3,796,416 
in  30  seconds,  and  many  instances  are  well  known.  (3) 
There  may  be  some  useful  hint  in  the  observation  which 
several  visitors  have  made,  that  the  answers  which  are 
stamped  out  quickly  and  energetically  are  usually  right. 
(4)  Numerous  mistakes  are  made,  especially  when  the 
pupil  is  cross  or  distracted.  It  is  of  interest  to  notice, 
what  Professor  Plate  and  others  have  pointed  out,  that 
the  number  of  mistakes  increases  with  the  difficulty  of  the 
sums.  There  was  often  a  curious  intelligibility  in  the 
mistakes,  though  an  expert  arithmetician  has  pointed 
out  that  the  nature  of  the  mistakes  tells  against  the  theory 
that  real  calculation  is  going  on.  That  the  horses  are  able 
to  correct  their  mistakes  is  also  of  interest.  Similarly, 
it  is  interesting  that  different  experts  who  visited  the 
horses  got  very  unequal  exhibitions  of  skill,  or  whatever 
it  may  be,  and  that  the  horses  have  refractory  periods 
when  they  won't  learn  or  won't  show  off.  The  fact  that 
'  Clever  Hans '  has  lost  all  interest  in  figures,  finds  its 
analogy  in  the  case  of  Richard  Whately,  whose  gifts  as  a 
calculating  boy  were  quite  replaced  by  others  by  the  time 
he  became  Archbishop  of  Dublin. 

What  is  to  be  said  on  the  other  side  ?     Many  have  pro- 
claimed their  opinion  that  there  must  be  some  trickery  some- 


THE  WAYS   OF   LIFE  261 

where,  but  this  remains,  on  the  whole,  a  vague  innuendo. 
There  is  no  evidence  whatever  that  Herr  Krall  is  other 
than  a  perfectly  honourable  and  absolutely  disinterested 
inquirer,  anxious  to  get  at  the  facts.  Turning  to  concrete 
objections,  we  find  that  unbelieving  critics  have  referred 
to  the  darkness  of  the  stable ;  to  the  mesmeric  influence 
of  Krall;  to  the  fact  that  the  horses  concentrate  their 
attention  on  their  master,  the  groom,  and  their  carrots, 
and  pay  little  heed  to  the  problem  on  the  board ;  to  the 
continuous  flow  of  remarks  addressed  to  the  horses  by  Krall 
in  varied  tones,  from  pianissimo  to  fortissimo ;  to  the  all 
too  constant  presence  of  the  groom,  Albert,  who  sometimes 
(according  to  Wigge)  touches  the  horses  suggestively ! 
Each  and  all  of  these  objections  must  be  fully  met  by 
further  investigation,  but  it  is  interesting  to  note  that 
many  of  them  have  been  already  met  by  particular 
experiments,  to  some  of  which  we  have  referred. 

We  have  stated  the  two  interpretations — each  beset 
with  difficulties.  On  the  extreme  sceptical  view,  the  horses 
stamp  out  an  answer  which  is  somehow  communicated 
to  them  by  some  practical  joker  who  can  compute  rapidly, 
and  who  must  be  having  the  time  of  his  life  reading  the 
literature  on  the  subject.  On  this  view,  which  is  beset 
with  great  difficulties,  the  horses  are  showing  remarkable 
sensitiveness  to  minute  signals  and  extraordinary  docility 
in  their  innocent  complicity.  It  is  plainly  the  task  of 
further  investigation  to  answer,  one  after  another,  all  the 
objections  which  unfriendly  critics  have  urged. 

On  the  other  view,  which  finds  no  evidence  of  trickery, 
the  results  seem  indeed  like  the  beginning  of  a  new  chapter 
in  Animal  Psychology.  The  horses  have  shown  not  only 
extraordinary  powers  of  precise  attention,  concentration, 


262  THE  WONDER  OF  LIFE 

association,  memory,  but  an  unsuspected  genius  for  dealing 
with  numbers.  Those  who  take  this  view  need  not,  of 
course,  accept  KralPs  generous  conclusion  that  his  horses 
think  as  men  do,  but  they  must  give  him  credit  as  an 
educator  who  has  been  rewarded  by  the  discovery  of 
remarkable  mental  powers  which  at  present  elude  analysis. 
In  any  case,  it  is  for  Comparative  Psychology  to  continue 
the  investigation  on  the  strictest  scientific  lines  and  with- 
out prejudice. 

A  lady  in  Mannheim  taught  her  Airedale  terrier  on  KralPs 
methods.  The  dog  learned  to  count  and  spell  like  Krall's 
horses.  Professor  H.  E.  Ziegler  reports  that  he  visited 
the  dog,  and  drew  on  a  piece  of  paper  a  mouse  (Maus),  a 
flower  (Blume),  and  an  elephant  (Elefant).  The  dog 
spelled  out  '  Maus ' ;  then  Bliml,  which  is  said  to  be  the 
local  dialect  for  Blume ;  and,  finally,  Kma  Krai  Brdo. 
The  last  was  very  puzzling,  but  it  seems  that  the  dog  had 
seen  several  days  before  a  postcard  of  Krall's  young 
elephant,  which  is  called  Kama.  Therefore,  when  shown 
Professor  Ziegler's  drawing,  it  spelled  out  Kma  Krai.  It 
may  be  that  Brdo  referred  by  some  association  of  ideas 
to  Krall's  blind  horse,  Berto.  As  no  one  knew  beforehand 
what  was  to  be  drawn,  it  is  difficult  to  suggest  that  the 
dog  was  coached  up,  and  we  have  Professor  Ziegler's  word 
for  it  that  unconscious  hints  and  trickery  cannot  be  thought 
of  for  a  moment. 


CHAPTER  V 

THE  WEB  OF  LIFE 

(INTRICACY  OF  INTER-KELATIONS) 

'Sbe  10  all  tbings.  Sbe  rewards  berself  anD  punisbes 
berself;  fs  ber  own  jog  anD  ber  own  misery.  .  .  .' 

4 1bcr  cbiiDren  are  numberless.  Co  none  is  sbe  altogether 
miserly ;  but  sbe  bas  ber  favourites,  on  wbom  sbe  squan&ers 
mucb,  anD  for  wbom  sbe  makes  great  sacrifices.' 

— Ooethe's  Aphorisms,  translated  by  Huxley. 

The  Balance  of  Nature — Linkages— The  Living  Earth — Mutual 
Dependence  for  the  Continuance  of  Life — Ants  and  Seeds — 
Mussels  and  Minnows — Bees  and  Flowers — Other  Illustrations 
— Inter-Relations  of  a  Pitcher-plant — Ants  and  Plants 
— Epizoic  Associations — Shelter  Associations — Commensalism — 
Symbiosis — Parasitism — Domestic  Complications — The  Cuc- 
koo's Habit^Animal  Societies— The  Ant  Hill— The  Bee  Hive 
— The  Termitary — Other  Illustrations — Domestication — Guests 
and  Pets — Slave- making — Man  and  the  Web  of  Life. 

ONE   of  Darwin's  master-ideas   has   during  the   last 
half -century  passed  into  general  intellectual  cur- 
rency— the  idea  of  the  web  of  life.     Nothing  is  unimportant, 
nothing  is  isolated,  nature  is  a  vast  system  of  inter-relations 
and  linkages.     Earthworms  have  made  most  of  the  fertile 
soil  of  the  Earth  ;  cats  have  to  do  with  next  year's  clover- 
crop  ;  eighty  seeds  may  germinate  from  one  clodlet  on  one 
bird's  foot.     These  are  Darwinian  instances  and  we  are 
263 


264  THE  WONDER  OF  LIFE 

constantly  discovering  new  ones  to-day.  Every  move  on 
Nature's  chessboard  has  consequences  which  may  have  a 
very  long- lasting  influence  on  the  game.  We  know  that  the 
housefly  puts  an  appreciable  drag  on  the  wheel  of  civiliza- 
tion, that  squirrels  affect  the  harvest,  that  wagtails  have 
to  do  with  the  success  of  sheep-farming,  and  that  cats  may 
play  a  not  unimportant  role  in  determining  the  welfare  of 
India. 

As  a  corollary  to  Darwin's  central  conception  came 
Pasteur's — the  idea  of  the  controllability  of  life.  Silk- 
worm disease  and  Phylloxera  among  the  vines  are  not  dis- 
pensations of  Providence  to  be  submitted  to,  they  are 
handicaps  to  be  got  rid  of.  Olive  pests  in  Italy  and  Vole 
plagues  in  Thessaly  do  not  arise  without  good  reason, 
and  it  is  within  our  powers  to  alter  these  reasons.  Tollitur 
causa,  ablatus  effectus. 


THE  BALANCE  OF  NATURE 

This  phrase  may  serve  to  indicate  the  broadest  kind  of 
inter-relation,  where  two  sets  of  living  creatures,  having 
evolved  together,  are  dependent  on  one  another,  and  on 
the  persistence  of  an  approximate  equilibrium  between 
them.  It  is  possible  to  construct  a  closed- off  aquarium 
in  which  the  plants  and  animals  balance  one  another  per- 
fectly for  a  period  varying  with  the  degree  of  uniformity 
in  external  conditions,  and  the  carefulness  of  adjustment 
between  the  diverse  constituents  of  the  population.  The 
oxygen  required  by  the  animals  is  produced  in  sunlight 
by  the  green  plants,  and  the  carbonic  acid  gas  produced 
by  the  animals  is  utilized  by  the  plants.  The  closed-off 
microcosm  usually  comes  to  an  end  by  an  over-production 


THE  WEB  OF   LIFE  265 

of  minute  plants  or  by  the  accumulation  of  poisonous  waste- 
products. 

Taking  a  less  artificial  instance,  we  recognize  the  depend- 
ence of  vegetarian  animals  on  the  plants  of  the  given  area. 
When  the  lemmings  of  a  Scandinavian  valley  or  the  voles 
further  south  multiply  exceedingly  in  times  of  plenty, 
they  tend  to  check  their  own  increase  by  eating  up 
every  green  thing.  Then  the  lemmings  go  on  the  march 
and  the  voles  spread  from  parish  to  parish. 

There  is  a  necessary  proportion  to  be  sustained  between 
herbivorous  animals  and  plants,  between  carnivorous 
animals  and  herbivores,  and  one  of  the  reasons  of  the 
ceaseless  struggle  for  existence  is  just  the  clashing  of  the 
requirements  of  different  kinds  of  creatures.  The  struggle 
goes  on  in  a  more  or  less  inconspicuous  sort  of  way  until 
some  environmental  cause,  such  as  peculiar  weather, 
brings  about  a  marked  disproportion  on  one  side  or  the 
other,  and  then  there  is  a  crisis. 

Attention  has  often  been  directed  to  the  'beneficent 
provision  of  Nature '  that  animals  which  are  preyed  upon 
are,  on  the  whole,  more  prolific  than  those  which  prey  upon 
them.  Thus,  small  Rodents  tend  to  be  much  more  prolific 
than  Carnivores.  The  primary  reason  for  this  is  probably 
that  less  individuated  types  tend  to  be  more  prolific.  In 
a  relatively  stupid  stock  the  variants  in  the  direction  of 
increased  reproductivity  will  tend  to  survive.  Great 
reproductivity  will  become  the  survival-securing  quality 
of  the  feeble-minded  types. 

Birds  keep  down  insects  and  small  mammals,  and  they 
also  distribute  seeds.  It  is  plain  that  any  sudden  reduc- 
tion in  their  numbers  will  bring  about  disharmony  in  the 
order  of  Nature.  Those  who  make  such  calculations 


266  THE  WONDER  OF  LIFE 

tell  us  that  in  the  absence  of  birds  the  earth  would  be 
quite  uninhabitable  in  six  years.  Certain  it  is  that,  as 
things  are  at  present,  the  vegetation  of  the  earth  depends 
on  birds.  The  grass  of  the  meadow  would  soon  be  gone 
if  birds  did  not  thin  the  grubs  in  the  winter  and  the  spring. 
The  trees  of  the  woods  would  not  long  remain  if  the  birds 
did  not  clean  off  the  injurious  insects.  The  small  rodents, 
such  as  mice,  popularly  called  vermin,  are  in  many  places 
bad  enough  as  it  is,  but  the  hawks  and  owls  save  us  from 
plagues.  No  one  can  deny  that  bullfinches  destroy  fruit- 
buds,  that  wood-pigeons  devour  large  quantities  of  grain, 
that  sparrow-hawks  destroy  many  useful  birds,  that 
sparrows  introduced  into  the  States  have  been  a  national 
curse,  and  so  on  ;  but  these  are  quite  exceptional  instances. 
Even  if  we  adhere  to  a  somewhat  narrow  anthropocentric 
position,  the  balance  of  beneficence  in  favour  of  all  but  a 
few  birds  is  overwhelmingly  great.  And  it  is  absurd  to 
suppose  that  Man,  like  a  spoiled  child  of  the  Universe, 
should  have  everything  made  smooth  for  him,  and  should 
have  no  taxes  to  pay  for  his  continual  interference  with  the 
established  order  of  things. 

Prof.  Alfred  Newton  once  drew  a  vivid  picture  of  the 
desolation  likely  to  be  wrought  by  man's  carelessness  in 
disturbing  the  balance  of  Nature — alike  by  introduction 
and  extermination. 

'  What  if  a  future  Challenger  shall  report  of  some  island, 
now  known  to  possess  a  rich  and  varied  animal  population, 
that  its  present  fauna  had  disappeared,  that  its  only  mam- 
mals were  feral  pigs,  goats,  rats  and  rabbits — with  an  infusion 
of  ferrets,  introduced  by  a  zealous  "  acclimatizer  "  to  check 
the  abundance  of  the  rodents  last  named,  but  contenting 
themselves  with  the  colonists'  chickens,  that  sparrows 


THE  WEB  OF  LIFE  267 

and  starlings,  brought  from  Europe,  were  its  only  land- 
birds,  that  the  former  had  propagated  to  such  an  extent 
that  the  cultivation  of  cereals  had  ceased  to  pay — the 
prohibition  of  bird-keeping  boys  by  the  local  school- 
master contributing  to  the  same  effect — and  that  the 
latter  (the  starlings),  having  put  an  end  to  the  indigenous 
insectivorous  birds  by  consuming  their  food,  had  turned 
their  attention  to  the  settlers'  orchards  so  that  a  crop 
of  fruit  was  only  to  be  looked  for  about  once  in  five  years 
— when  the  great  periodical  cyclones  had  reduced  the 
numbers  of  the  depredators,  that  the  goats  had  destroyed 
one-half  of  the  original  flora,  and  the  rabbits  the  rest, 
that  the  pigs  devastated  the  potato-gardens  and  yam- 
grounds.' 

The  destruction  of  small  bats  seems  to  be  entirely  wanton 
and  foolish,  for  they  help  birds  in  thinning  the  hosts  of 
fecund  insects.  It  has  been  recently  stated  by  Dr.  C.  A.  R. 
Campbell,  of  San  Antonio,  Texas,  that  there  is  an  apparent 
relation  between  mosquitoes  and  bats,  that  the  former 
increase  as  the  latter  decrease.  He  suggests  the  estab- 
lishment of  shelters  for  the  bats  so  that  they  may  increase 
and  multiply. 

Linkages. — At  every  turn  the  naturalist  finds  proof  that 
Nature  is  a  vast  system  of  linkages,  and  that  it  is  quite 
unscientific  to  think  of  any  organism  as  trivial  or  detached. 
The  arc  of  its  life  may  not  enter  the  human  field,  but  it  is 
sure  to  enter  many  others,  and  one  or  other  of  its  inter- 
sections may  at  any  moment  acquire  significance  for  Man. 
One  would  not  be  inclined  at  first  sight  to  attach  much 
practical  importance  to  the  sea-gooseberries  or  Ctenophores, 
pelagic  animals  of  the  greatest  delicacy  and  beauty.  They 
descend  into  quiet  water  when  there  is  any  sea  on ;  they 
re-ascend  when  there  has  been  a  lasting  calm.  Their 


268 


THE  WONDER   OF  LIFE 


importance    lies    in  the    fact    that    they    destroy   large 
numbers  of  floating  fish  eggs  and  young  fry.    Dr.  A.  G. 

Mayer  writes  : — 

'  Tender  as  they  are 
to  the  touch,  passing 
jelly-like  between  the 
fingers  of  the  hand 
that  attempts  to  seize 
them,  their  food  con- 
sists largely  of  young 
fishes,  which  they  en- 
gulf in  great  numbers, 
seizing  their  prey  by 
means  of  their  pecu- 
liar adhesive  cells. 
Thus,  in  the  cold 
northern  waters  where 
ctenophores  occur  in 
vast  swarms,  they 
constitute  a  serious 
menace  to  the  cod 
fisheries  by  devouring 
pelagic  eggs  and 
young  fish.' 

In  almost  all  cases 
the  ordinary  stinging 
cells  characteristic  of 
jelly-fishes  and  other 
Coelenterates  are  ab- 

Fio.  45. — Ctenophore  showing  (T)  retractile  ,  f__m  nfPTvnn>ir»rpfl 

tentacles  bearing  adhesive  cells;  (M)  sent  from Ltenopnores, 
position  of  the  mouth ;  (c)  line  of  font  their  place  Is  taken 
ciliated  combs ;  (AS)  apical  spot  with  ,  ..  , 

a  sensory  organ.     (After  Mayer.)  by    equally  Character- 


THE   WEB   OF  LIFE  269 

istic  adhesive  cells  which  grapple  with  small  animals  pass- 
ing by. 

Another  good  instance  of  linkage,  which  is  not  obvious 
at  first  glance,  is  the  connexion  between  fishes  and  malaria. 
But  it  is  not  a  hard  riddle  to  read.  The  parasite  which 
causes  malaria  is  disseminated  by  the  mosquito,  and  the 
larval  mosquitoes  are  devoured  by  many  fishes.  Captain 
R.  B.  Seymour  Sewell  and  B.  L.  Chaudhuri  have  described 
eleven  Indian  fishes  which  are  of  proved  value  as  mosquito 
destroyers.  They  conclude  that  '  fishes  may  be  a  very 
important  agent  in  regulating  and  diminishing  the  degree 
of  malarial  infection  in  any  given  district '.  It  has  also 
been  suggested  that  the  reason  why  the  Barbadoes  are 
remarkably  free  from  malaria,  is  that  the  mosquito  larvse 
are  devoured  in  large  numbers  by  a  small  fish,  popularly 
known  as  '  millions',  which  is  very  abundant  in  all  the 
streams  and  pools. 

The  practical  lesson  to  Man  is  the  obvious  one  that  he 
cannot  be  too  careful  lest  he  disturb  the  balance  of  things, 
by  extermination  on  the  one  hand,  or  by  transplantation 
on  the  other.  We  have  elsewhere  referred  to  important 
instances,  such  as  the  introduction  of  rabbits  into  Australia 
and  of  house-sparrows  into  the  United  States.  We  may 
refer  again  to  the  story  of  the  rats  of  Jamaica.  Rats 
brought  by  ships  became  a  plague  in  Jamaica.  To  cope 
with  them  the  mongoose  (Herpestes  griseus)  was  imported, 
and  it  made  short  work  both  of  the  Old  World  rats  and  the 
Jamaican  cane-rats.  But  when  these  were  gone,  the 
appetite  of  the  mongoose  remained,  and  the  poultry  and 
various  ground  birds  began  to  suffer.  Useful  insect-eating 
lizards  were  also  eaten,  and  another  cloud  rose  on  the  sky — 
there  was  a  multiplication  of  injurious  insects  and  ticks, 


270  THE  WONDER  OF  LIFE 

so  that  plants  and  animals  began  to  be  afiected  through 
an  ever-widening  circle. 

Mr.  Thomas  Barb  our  has  followed  up  the  chain  of  con- 
sequences as  regards  reptiles  : — 

'  The  introduction  of  the  mongoose  has  caused  the  almost 
complete  extinction  of  many  species  which  were  once 
abundant,  and  has  in  some  ways  radically  changed  the 
facies  of  the  fauna.  In  the  back  country,  lizards  are  rarely 
met  with,  and  it  is  only  in  the  vicinities  of  villages  and 
towns,  where  they  are  more  or  less  protected,  that  one 
may  obtain  satisfactory  series  of  many  species.  The 
true  ground-inhabiting  forms  have,  of  course,  suffered 
most,  so  that  lizards  of  the  genera  Ameiva,  Mabuia  and 
Celestus  are  now  scarce  and  difficult  to  obtain.  Snakes 
have  suffered  perhaps  more  than  lizards.' 

An  additional  linkage  in  the  case  of  the  sparrow  intro- 
duced into  the  United  States  has  recently  come  to  light, 
but  it  requires  further  investigation.  The  swarms  of 
sparrows  drive  away  other  birds,  but  they  also  appear  to 
exert  an  inimical  influence  on  poultry  in  the  wide  sense 
(fowls,  turkeys,  ducks,  geese,  etc.).  In  the  sparrow's 
intestine  there  are  parasitic  Protozoa,  known  as  Coccidia, 
which  occur  in  great  abundance.  The  sparrow  is  accus- 
tomed to  them,  but  when  they  pass  to  new  hosts,  such  as 
poultry,  they  cause  serious  diseases,  known  as  '  blackhead  ' 
or  coccidiosis.  The  parasites  also  occur  in  the  American 
'  robin '  (Merula  migraloria),  the  quail,  and  the  Ruffed 
Grouse  ;  and  perhaps  there  is  a  risk  of  making  the  sparrow 
a  scapegoat. 

The  Living  Earth. — As  an  instance  of  subtle  inter- 
relations, we  may  refer  to  some  recent  investigations  at  the 
Rothamsted  laboratory.  Drs.  Russell  and  Hutchinson 


THE   WEB   OF   LIFE  271 

found  that  when  soils  were  heated  or  when  they  were  dosed 
with  certain  volatile  antiseptics,  and  afterwards  brought 
into  conditions  favourable  for  plant  growth,  they  showed  a 
great  increase  in  fertility.  Further  inquiry  showed  that  the 
soil  Bacteria  are  first  reduced  in  numbers  by  the  heating 
or  sterilizing,  and  that  after  a  while  they  increase  enor- 
mously. To  this  increase  is  due  a  greater  production  of 
ammonia  in  the  soil,  and  to  this,  of  course,  the  greater 
fertility.  But  the  puzzle  is  why  the  decrease  after  heating 
or  sterilizing  should  be  followed  by  a  great  increase. 

The  suggested  solution  of  the  puzzle  is  very  interesting, 
and  it  is  instructive  even  though  it  may  require  subsequent 
modification.  There  are  many  Protozoa  in  the  soil,  some 
of  which  feed  on  Bacteria  and  thus  limit  their  increase. 
The  Protozoa  are  more  sensitive  than  the  Bacteria  to  the 
heating  or  sterilizing.  There  is  a  killing  off  in  both  camps, 
but  the  Protozoa  suffer  most.  In  the  period  of  recovery 
the  surviving  Bacteria  multiply  enormously  in  the  relative 
absence  of  their  enemies.  This  solution  requires  verifica- 
tion, and  our  knowledge  of  the  soil  Protozoa  is  still  too 
scanty  and  vague.  A  great  reward  certainly  awaits  the 
investigator  of  the  Protozoa  of  the  soil.  Mr.  T.  Goodey 
has  listed  about  thirty  already,  but  eighteen  of  these  are 
ciliated  Infusorians  which  exist  in  the  soil  in  an  encysted, 
not  in  an  active  state,  and  cannot  therefore  function  as 
Bactericides. 


MUTUAL  DEPENDENCE  FOB  THE    CONTINUANCE  OF  LIFE 

Two  organisms  inhabiting  the  same  area  may  become 
linked  together  in  such  a  way  that  the  continuance  of  the 
life  of  one  of  the  two  is  dependent  on  the  presence  of  the 


272  THE  WONDER  OF  LIFE 

other.  Thus  many  flowers  depend  for  their  pollination 
on  the  visits  of  quite  definite  insects,  who,  in  minding  their 
own  business  of  collecting  pollen  and  nectar,  unconsciously 
transfer  the  fertilizing  dust  from  blossom  to  blossom.  We 
shall  return  to  this  particular  case  after  we  have  noted  a 
few  other  illustrations. 

Fruit-eating  birds,  such  as  thrushes,  are  responsible  for 
the  distribution  of  many  seeds.  Many  water-birds  carry 
minute  animals  from  one  watershed  to  another,  and 
there  is  indeed  quite  a  fauna  and  flora  of  birds'  feet. 
Earthworms  sometimes  plant  trees  and  the  squirrel's 
forgotten  stores  may  serve  to  start  a  coppice.  The  world 
is  full  of  such  linkages.  We  may  refer  to  the  role  of 
ants  as  a  less  familiar  illustration. 

Ants  and  Seeds.— It  has  been  known  for  a  long  time 
that  ants  carry  to  their  nests  the  seeds  of  the  cow-wheat 
(Melampyrum),  and  it  has  been  suggested  that  in  doing  so 
they  labour  under  a  '  misapprehension  ',  as  one  might  say, 
confusing  them  with  pupae.  There  are  some  details  which 
support  this  view,  which  may  have  something  in  it. 
Probably,  however,  the  ants  know  better,  and  the 
theory  does  them  injustice.  For  further  research  has 
shown  that  ants  have  a  very  marked  predilection  for 
certain  seeds  and  fruits,  and  carry  them  about  for  great 
distances. 

Experiment  has  shown  that  ants  are  particularly  fond  of 
seeds  which  have  '  food-bodies  '  or  '  oil-bodies  '  in  their 
coats,  such  as  violet,  bluebell,  mignonette,  and  fumitory. 
In  many  cases  the  ants  carry  the  seeds  to  the  nests,  but  eat 
only  the  external  food-bodies,  so  that  the  thrown-out  seeds 
may  still  germinate.  Moreover,  in  many  cases  the  seeds 
are  lost  by  the  ants  on  their  journeyings.  Prof,  F,  E, 


THE  WEB   OF  LIFE  273 

Weiss  took  the  seeds  of  the  gorse,  which  have  a  bright 
orange,  fleshy  food-body,  and  placed  them  on  ant-tracks. 
He  found  that  they  were  rapidly  picked  up  by  the  ants, 
while  seeds  of  various  other  plants  were  left  alone.  The 
seeds  of  the  broom,  which  have  a  food-body  like  that  of  the 
gorse,  were  treated  in  the  same  way.  It  seems  legitimate, 
then,  to  conclude  that  ants  assist  in  the  distribution  of  gorse 
and  broom. 

Mussels  and  Minnows. — The  freshwater  Mussels  (Unio 
and  Anodon)  are  bound  up  in  the  bundle  of  life  with  fishes, 
such  as  minnow  and  stickleback.  The  mussel  keeps  its 
larvae  in  a  capacious  cradle  within  the  outer  gill-plate,  and 
does  not  allow  them  to  escape  until  a  minnow  or  the  like 
comes  into  the  immediate  vicinity.  When  the  crowd  of 
free-swimming  bivalve  larvae  find  themselves  in  the  water 
near  the  fish  they  show  manifest  excitement  and  move 
towards  it,  snapping  their  valves,  which  bear  minute  attach- 
ing hooks.  Fine  anchoring  threads  of  a  glutinous  character 
are  also  exuded,  and  attachment  is  effected  to  the  minnow's 
skin.  For  a  considerable  time  the  larvae  remain  fixed  to 
the  fish,  pass  through  a  kind  of  metamorphosis,  and  eventu- 
ally fall  off  into  the  mud — perhaps  far  from  the  place  where 
their  parents  lived.  There  are  many  interesting  points 
here — the  hereditary  attraction  of  the  mussel  larvae  to  the 
fish  (in  the  laboratory  they  are  excited  by  even  a  piece  of 
fish),  the  special  adaptations  which  secure  attachment, 
the  metamorphosis,  the  distribution ;  but  what  we  wish  to 
emphasize  is  the  broad  fact  that  two  creatures  as  different 
as  possible — the  mussel  and  the  minnow — have  got  linked 
up  together.  The  minnow  is  quite  passive  in  this  linkage, 
but  it  is  an  extremely  interesting  fact  that  a  continental 
fish,  the  bitterling  (Rhodeus  amarus},  should  spend  part  of 


274  THE  WONDER  OF  LIFE 

its  early  life  as  a  semi-parasite  inside  the  gill-cavity  of  the 
freshwater  mussel. 

Bees  and  Flowers. — The  inter-relations  between  bees 
and  flowers  have  formed  the  subject  of  many  studies  and  of 
many  controversies.  For  the  matter  is  not  so  clear  and 
simple  as  is  sometimes  represented.  Bees  visit  the  flowers 
for  the  pollen  and  the  nectar.  The  cane-sugar  of  the  nectar 
is  transformed  into  glucose  and  is  consumed  as  food  by  its 
collector,  or  is  stored  in  cells.  The  pollen  serves  as  food 
directly,  or  it  is  mixed  with  honey  to  form  a  nutritive 
paste  or  jelly  for  the  young.  In  hive-bees  there  is  often  a 
good  deal  of  method  in  the  collecting ;  Aristotle  noted 
rightly  that  they  often  keep  to  one  kind  of  flower  at  a  time. 
There  is  often  division  of  labour  among  the  workers,  for 
some  collect  nectar  and  others  collect  pollen.  The  adapta- 
tions on  the  bees'  part  are  many,  but  the  most  important 
are  the  suctorial  mouth-parts  and  the  pollen-collecting 
hairs  on  the  legs. 

The  egg-cell  of  a  flowering  plant  hidden  away  within 
the  ovule  within  the  ovary  does  not  usually  develop  into 
an  embryo  unless  it  be  fertilized  by  a  male  element  (nucleus) 
within  the  pollen  grain.  The  pollen  grains  are  dusted  on 
to  the  stigma  of  the  pistil  in  various  ways — usually  by 
insects  or  by  the  wind  or  by  shaking — and  from  a  pollen 
grain  a  pollen-tube  grows  down  in  search  of  the  egg-c3ll. 
It  is  a  nucleus  within  the  pollen-tube  that  effects  the  fertili- 
zation proper  and  sets  development  agoing.  Unless  this 
happens,  the  ovules  or  possible  seeds  do  not  become  real 
seeds  containing  embryos. 

Now  it  is  well-known  that  although  self-fertilization 
occurs  (e.g.  in  peas),  cross-fertilization  is  predominant. 
That  is  to  say,  fertilization  is  usually  effected  by  pollen 


THE   WEB   OF  LIFE  275 

from  another  plant,  and  sometimes  that  is  the  only  possible 
mode.  It  was  one  of  Darwin's  great  services  that  he  showed 
by  experiment  the  advantages  of  cross-fertilization  as 
against  self-fertilization  where  that  is  possible.  The  plants 
that  grow  from  cross-fertilized  seeds  are  more  robust,  tend 
to  flower  earlier,  and  have  more  numerous  and  better  seeds. 
In  Mexico  the  vanilla  is  cross-pollinated  by  bees  ;  in  other 
regions  the  stamen  is  rubbed  against  the  pistil  artificially  ; 
there  is  said  to  be  no  doubt  as  to  the  superiority  of  the 
Mexican  vanilla.  Darwin  also  pointed  out  the  interesting 
fact  that  if  there  be  placed  on  a  stigma  a  pollen  grain  from 
the  same  flower  and  a  pollen  grain  from  another  plant  of  the 
same  species,the  pollen-tube  of  the  latter  grows  more  rapidly 
and  usually  wins  the  race  for  the  ovum.  If  the  conclusion 
be  accepted  that  cross-fertilization  is  the  advantageous 
mode,  then  the  importance  of  bees  and  other  flower- visiting 
insects  is  plain,  for  it  is  they  who  unconsciously  effect  the 
pollination.  On  their  visits  to  flowers  various  parts  of  their 
bodies  are  dusted  with  pollen  from  the  stamens,  and  when 
they  pass  on  to  other  flowers  of  the  same  species  they 
mechanically  and  inevitably  transfer  the  pollen  to  the 
stigmas. 

If  the  bees  are  useful  to  the  races  of  flowering  plants 
which  they  visit,  as  experiment  proves,  and  if  the  flowers 
are  useful  to  the  bees,  as  is  evident,  then  we  should  on 
general  grounds  expect  to  find  a  variety  of  adaptations 
fitting  the  bees  to  make  the  most  of  the  flowers  and  fitting 
the  flowers  to  make  the  most  of  the  bees.  That  is  what  is 
found,  and  it  is  very  instructive  to  notice  that  there  is,  so 
to  speak,  a  long  inclined  plane  of  adaptiveness,  some  bees 
being  much  fitter  flower-visitors  than  others,  and  some 
flowers  making  much  more  of  the  bees  than  do  others. 


276  THE  WONDER  OF  LIFE 

The  climax  of  bee  evolution  is  exhibited  by  the  hive-bees 
(Apis  mellifica),  which  we  mention  in  the  plural  because 
there  are  a  good  many  varieties  which  again  differ  in  their 
degrees  of  fitness.  The  especial  fitness  of  the  hive-bee  is 
to  be  found  in  the  perfection  of  the  arrangements  for  col- 
lecting and  carrying  the  pollen  and  for  sucking  the  nectar. 
It  is  interesting  to  find  that  apiarists  have  for  years  prac- 
tised some  measure  of  selection  with  the  hive-bee,  just  as 
the  breeder  with  his  horses  and  cattle,  paying  special 
attention  to  such  points  as  the  length  of  the  tongue  (which 
they  measure  with  a  glossometer  !) — the  desire  being  to 
control  its  length. 

The  controversy  really  begins  when  we  inquire  into  the 
adaptiveness  of  the  flowers  to  their  visitors,  for  there  is  one 
school  of  naturalists  who  insist  in  interpreting  floral  char- 
acters as  the  outcome  of  a  selective  process  in  which  insacts 
have  played  the  leading  role,  while  according  to  another  the 
selective  role  of  insects  is  of  quite  subsidiary  importance. 

The  extreme  position  in  regard  to  the  role  of  insects  was 
long  since  expressed  by  the  late  Lord  Avebury,  then  Sir 
John  Lubbock. 

'  Not  only  have  the  form  and  the  colours,  the  bright 
tints,  the  sweet  odours  and  the  nectar  been  gradually 
developed  by  force  of  an  unconscious  selection  exercised 
by  the  insects,  but  even  the  arrangement  of  the  colours, 
the  shape,  the  size  and  the  position  of  the  petals,  the  rela- 
tive position  of  the  stamens  and  pistil,  are  all  determined 
by  the  visits  of  the  insects,  and  in  such  a  way  as  to  assure 
the  great  object  (fertilization)  that  these  visits  are  intended 
to  effect.' 

The  famous  French  botanist,  Gaston  Bonnier,  has  been 
foremost  in  maintaining  that  the  plant  secretes  nectar  for 


THE  WEB   OF  LIFE  277 

its  own  use,  and  would  secrete  nectar  were  there  no  bees. 
The  nectaries  are  manufactories  where  cane-sugar  (due  to 
the  starch  made  in  the  leaves)  is  worked  up  and  stored — 
usually  for  the  fruits  and  seeds.  The  drops  that  are  sweated 
out,  as  night  falls,  from  the  nectaries  never  contain  more 
than  a  small  part  of  the  sugar  of  the  nectaries  ;  they  cor- 
respond to  water-drops  elsewhere,  except  that  they  are  more 
or  less  rich  in  sugar ;  if  insects  do  not  suck  them  up  they 
are  re-absorbed  in  due  course.  This  appears  to  be  a  very 
effective  objection  up  to  a  certain  point.  It  shows  that 
the  primary  significance  of  the  nectaries  is  for  the  plant 
itself.  We  wish  to  point  out,  however,  a  rule  in  scientific 
method  which  has  its  application  here,  namely,  that  one 
must  be  careful  not  to  mix  up  problems  of  origin  with 
problems  of  subsequent  evolution.  Bonnier's  evidence  that 
the  primary  significance  of  nectaries  is  for  the  plant  itself, 
is  not  inconsistent  with  the  view  that  bees  and  other 
insects  may  have  had  something  to  do  with  the  evolution  of 
these  organs,  e.g.  in  determining  their  precise  position. 
It  remains  a  fact  that  bees  tap  them,  and  it  is  probable 
that  these  visits  of  bees  have,  in  the  course  of  ages,  had 
some  selective  influence  on  the  plants. 

In  regard  to  the  fragrance  of  flowers  the  case  is  just  a 
little  different.  It  cannot  be  said  that  the  fragrance  as 
such  is  of  direct  use  to  the  flowers.  It  may  be  a  quite 
incidental  property  of  chemical  substances  which  are 
important  in  the  metabolism  of  the  plant.  But  in  the 
same  way  it  may  be  argued  that  the  sweetness  of  nectar  is 
not  as  sweetness  of  direct  use  to  the  plant.  The  sugar  need 
not  have  been  sweet,  and  the  chemical  substances  referred 
to  need  not  have  been  aromatic.  As  it  appears  to  us,  clear- 
ness comes  when  we  separate  the  two  problems — of  origin 


278  THE  WONDER  OF  LIFE 

and  of  subsequent  evolution.  The  answer  to  the  question 
of  the  origin  of  substances  of  sweet  odour  is  to  be  found 
in  the  physiological  study  of  the  plant.  But  the 
subsequent  success  of  flowering  plants  with  particular 
odours  may  have  been  due  to  the  fact  that  these  odours 
attracted  useful  insect  visitors  and  repelled  intruders. 
There  is  no  doubt  that  bees  are  attracted  by  the  fragrance 
of  honey  and  of  certain  flowers.  Bouvier  quotes  the 
pretty  observation  of  Perez  that  bees  frequenting  the 
willow  catkins  in  the  early  Spring  are  always  to  be  seen 
coming  from  the  side  toward  which  the  wind  blows  the 
fragrance. 

Thirdly,  there  is  the  question  in  regard  to  colour,  which 
is  the  most  difficult  of  the  three.  For  while  it  is  certain 
that  bees  like  sweetness,  and  that  bees  like  certain  odours, 
it  does  not  seem  so  certain  as  was  once  supposed,  that  bees 
like  particular  colours.  There  are  some  difficulties.  Bon- 
nier put  a  row  of  painted  blocks — red,  green,  white  or 
yellow — on  the  turf  near  some  hives  and  baited  each  with 
honey.  They  were  visited  impartially  by  the  bees,  but 
with  a  slight  preference  for  green.  It  is  said,  however, 
that  when  bees  are  preoccupied  with  flower- visiting  they 
do  not  pay  much  heed  to  other  things.  It  must  also  be 
remembered  that  the  flower  is  to  the  bee  a  complex  of 
sensations  appealing  to  sight  and  smell  and  taste ;  and 
that  in  trying  to  get  at  the  truth  by  analysis  one  may  land 
in  fallacy. 

Forel  put  coloured  artificial  flowers  in  a  basket  of  dahlias 
and  baited  them  with  honey.  The  bees  kept  to  the  dahlia 
till  an  inquisitive  or  blundering  individual  discovered  the 
treasure  in  the  artificial  flowers.  These  were  then  thor- 
oughly explored,  except  the  green  ones.  Even  after  the 


THE   WEB   OF   LIFE  279 

honey  had  been  removed  the  visits  continued — perhaps 
because  of  pleasant  memories. 

Some  interesting  experiments  made  by  J.  Wery  go  to 
show  that  colour  and  form  of  the  flowers  count  for  much. 
He  removed  the  corollas  from  a  number  of  flowers  and  left 
others  uninjured.  The  position  of  the  flowers  was  changed 
from  time  to  time.  In  the  one  experiment,  in  the  month  of 
June,  the  uninjured  flowers  were  visited  by  107  insects,  of 
which  72  were  bees  ;  the  flowers  without  corollas,  but  still 
conspicuous,  were  visited  by  79  insects,  of  which  28  were 
bees.  He  also  found  that  artificial  flowers  were  freely 
visited  and  that  a  glass  vessel  with  honey  was  left  alone. 
In  all  these  experiments  there  is  the  defect  that  they  deal 
with  bees  who  have  already  established  associations. 
Crucial  experiments  should  be  made  with  inexperienced 
bees. 

In  regard  to  colour,  our  conclusion  is  as  before.  The 
origin  of  the  coloured  substances  is  a  physiological  secret 
of  the  plant,  but  in  so  far  as  the  colour  has  formed  an  im- 
portant part  (how  important  remains  to  be  proved)  of 
the  complex  of  attractions  which  draw  the  useful  insect- 
visitors,  in  so  far  it  will  tend  to  persist  and  perhaps  increase 
in  the  course  of  selection.  But  there  can  be  little  hesita- 
tion in  accepting  Claude  Bernard's  general  conclusion  : — 

'  The  law  of  the  physiological  finality  is  in  each  individual 
being  and  not  outside  it ;  the  living  organism  is  made 
for  itself  ;  it  has  its  own  intrinsic  laws.  It  works  for  itself 
and  not  for  others.' 

Spoiling  an  Adaptation. — It  is  well  known  that  the 
common  Bombus  terrestris  is  very  much  given  to  biting  a 
hole  through  the  base  of  the  flower  of  the  red  clover,  and 


280  THE  WONDER  OF  LIFE 

is  therefore  of  little  or  no  use  in  pollination.  The  other 
species  of  humble-bees  enter  by  the  mouth  of  the  flowers, 
and  it  is  their  visits  that  really  count.  Mr.  Thomas  Belt 
made  the  interesting  observation  that  in  the  beginning  of 
the  season  some  individuals  of  Bombus  terrestris  visit  the 
flowers  of  the  scarlet-runner  in  a  legitimate  manner,  but 
soon  discover  that  there  is  a  shorter  way  by  biting  a  hole. 
They  burgle  unopened  buds  in  the  same  way,  and  the 
hive-bee  has  learned  to  utilize  the  humble-bee's  perfora- 
tions. Large  gaping  flowers  such  as  those  of  Foxglove 
and  Nasturtium  are  pollinated  by  Bombus  terrestris,  but 
the  narrower  ones  are  cut  through  and  despoiled  without 
benefit. 

The  Case  of  the  Fig. — Of  all  the  mutual  relationships 
that  are  involved  in  pollination,  those  concerned  with  the 
fig  are  perhaps  the  most  remarkable.  The  whole  story 
has  not  yet  been  cleared  up,  and  it  is  too  complex  for  full 
discussion  here.  Utilizing  a  luminous  article  by  Prof.  F. 
Cavers,  we  shall  simply  seek  to  explain  the  intricate  part 
which  certain  minute  wasps  play  in  the  fertilization.  As 
is  well  known,  the  flowers  of  the  fig  are  formed  within  a 
hollow,  pear-shaped  receptacle  with  a  narrow  mouth.  Just 
below  the  mouth  are  the  male  flowers  ;  the  rest  of  the  cavity 
is  lined  by  the  female  flowers  ;  all  are  very  minute.  Early 
in  Spring  a  female  wasp  (usually  Blastophaga  grossorum) 
enters  the  cup  of  the  early  inedible  inflorescences  of  the 
wild  fig  before  the  male  flowers  are  open,  and  lays  her  eggs 
in  the  female  flowers.  These  eggs  hatch  into  wingless 
males  who  never  escape  and  winged  females  who  fly  away 
after  they  have  been  fertilized  by  the  males.  As  they  creep 
out  they  get  dusted  with  pollen  from  the  male  flowers 
which  have  meantime  opened.  They  visit  a  later  crop  of 


THE  WEB   OF  LIFE  281 


figs,  and  the  female  flowers,  saved  by  long  styles  from 
having  eggs  laid  in  them,  are  pollinated  and  produce  normal 
seeds.  The  female  wasps  go  in  and  out  till  the  swelling  of 
the  juicy  inflorescence  nearly  closes  the  opening.  They 
then  migrate  in  autumn  into  small  late  inedible  figs,  where 
they  lay  eggs.  These  eggs  hatch  into  wingless  males  and 
winged  females,  which  remain  inside  the  small  figs  through 
the  winter.  The  females  escape  in  Spring  before  the  dry 
figs  fall  off,  and  then  the  story  begins  again.  We  must  not 
pursue  the  matter  further  :  it  is  complicated  by  the  exist- 
ence of  two  cultivated  varieties  of  the  wild  fig — the  inedible 
caprificus  with  male  flowers  only,  and  the  ordinary  edible 
domestica  with  female  flowers  only.  Both  are  visited  by 
the  Blastophaga  wasp. 

OTHER  RELATIONS  BETWEEN  PLANTS  AND  ANIMALS 

Many  animals  feed  on  plants  ;  many  animals  have  their 
home  on  or  in  plants  (see  Parasitism)  ;  many  animals  secure 
the  pollination  of  flowers  and  the  distribution  of  seeds ; 
a  few  animals  hide  themselves  with  a  disguise  of  plants  (see 
Masking) ;  a  few  animals  have  entered  into  an  internal 
partnership  with  plants ;  but  this  list  does  not  by  any 
means  suffice  to  cover  the  extraordinary  diversity  of  inter- 
relations. Let  us  refer  to  a  few  of  the  many  other  kinds 
of  linkage. 

Alga  on  Sloth's  Hair. — A  quaint  association  seems  to 
have  become  established  between  a  unicellular  Alga,  like 
the  Pkurococcus  which  makes  tree-stems  green  in  wet 
weather,  and  the  shaggy  hairs  of  the  South  American  sloth 
(Bradypus),  which  lives  an  altogether  arboreal  life.  The 
sloth  has  almost  exactly  the  same  greyish-green  colour  as 


282  THE  WONDER  OF  LIFE 

Tillandsia  usneoides,  the  so-called  '  vegetable  horse-hair  ', 
which  is  common  on  trees,  and  it  is  almost  certain  that  this 
colour-resemblance  has  protective  value. 

Ambrosia. — In  the  tunnels  made  by  various  beetles 
(e.g.  species  of  Xyloterus  and  the  like)  in  the  bark  and 
wood  of  trees  there  is  a  lining  of  Fungus,  which  produces 
special  spherical  '  ambrosia  '  cells,  serving  as  food  for  the 
insects.  This  association  appears  to  be  useful  to  both 
organisms  :  the  insects  are  fond  of  the  '  ambrosia  ' ,  and 
its  growth  makes  up  for  the  frequently  poor  nutritive 
quality  of  the  wood ;  the  fungi  profit  because  the  larvae 
carry  them  in  their  borings  into  the  sapwood,  where  they 
get  the  best  food  and  have  at  the  same  time  a  good  supply 
of  air.  The  association  has  been  carefully  studied  by  Prof. 
Neger,  who  regards  it  as  a  genuine  symbiosis.  It  is  much 
commoner  in  warm  and  tropical  zones,  where  the  boring 
insects  often  do  much  harm  both  by  their  own  operations 
and  by  introducing  the  fungi,  most  of  which  seem  to  be 
related  to  the  Ascomycete  genus  Endomyces.  The  matter 
may  become  more  complicated — wheels  within  wheels 
again — when  weeds  begin  to  grow  in  the  fungus  garden 
in  the  form  of  yeasts  and  Bacteria  and  the  like  which  further 
infect  the  wood,  but  are  not  of  any  use  to  the  beetles. 

Neger  found  the  same  '  ambrosia- cells  '  inside  the  galls 
made  by  certain  mites  (Asphondylia).  The  cavity  of  the 
gall  is  lined  by  a  layer  of  fungus  threads,  among  which  are 
the  special  '  ambrosia  cells '  which  the  developing  mites 
eat.  After  the  mites  have  departed,  the  spores  of  the 
fungus  are  produced  on  the  outer  surface  of  the  gall. 
Here,  then,  there  is  a  triple  combination  of  flowering-plant, 
mite,  and  fungus. 

Plants  Turning  the  Tables. — Even  the  worm  will 


THE   WEB   OF  LIFE  283 

turn  and  even  the  plant  may  retaliate.  Many  plants  are 
full  of  deadly  poison ;  many  are  densely  infiltrated  with 
crystals  from  which  even  snails  turn  aside ;  many  have 
thorns  and  spines  which  though  primarily  expressions  of 
peculiarities  of  constitution  are  often  secondarily  protec- 
tive ;  many  have  moats  and  railings  which  entrap  or  ward 
off  unwelcome  insect  visitors  ;  and  so  on  through  a  long 
list. 

More  actively  retaliatory  are  the  carnivorous  plants,  like 
the  butterwort  (Pinguicula),  which  attracts  insects  to  its 
glistening  glandular  leaf  and  there  digests  them,  like  the 
bladderworts  (Utricularia)  with  their  neat  traps  for  water- 
fleas,  like  the  sundews  (Drosera)  with  their  finger-like 
tentacles,  like  the  pitcher-plants  (Nepenthes  and  Sarracenia), 
catching  very  passively,  and  Venus' s  Fly-Trap  (Dionced), 
capturing  very  actively,  and  so  forth.  Here  there  is  a 
definite  turning  of  the  tables. 

A  hint  of  the  retaliatory  power  of  the  plant  is  familiar 
in  the  stinging  nettle  (Urtica  dioica),  with  its  hairs  contain- 
ing formic  acid,  but  the  capacity  reaches  its  climax  in  a 
large  member  of  the  order  Urticaceae,  the  '  stinging-tree ' 
(Laportea),  species  of  which  occur  in  Japan,  Eastern  India 
and  Queensland.  A  light  touch  of  a  leaf  produces  a  viru- 
lent effect  lasting  for  days  or  even  months.  The  pain  is 
described  by  men  who  have  been  stung  as  maddening  and 
agonizing,  and  the  effect  on  horses  and  dogs  is  also  very 
severe.  The  Australian  species  may  attain  a  height  of 
10-15  feet  and  is  said  to  emit  a  disagreeable  odour. 

Inter -Relations  of  a  Pitcher  Plant. — Let  us  take  one 
case  in  more  detail.  In  studying  one  of  the  insectivorous 
plants,  the  Spotted  Trumpet-Leaf,  Sarracenia  variolaris, 
whose  long  tube  forms  a  very  effective  trap,  Prof.  C.  V. 


284  THE  WONDER  OF  LIFE 

Riley  discovered  that  there  were  two  common  insect 
visitors,  that  came  and  went  and  were  not  destroyed.  One 
of  these  is  a  flesh-fly  (Sarcophaga  sarracenice),  which  is 
attracted  by  the  odour  of  putrescence  and  deposits  its 
maggots  (it  is  viviparous)  in  the  rotting  material,  with 
remains  of  ants,  flies,  moths,  beetles,  katydids,  crickets, 
and  the  like,  at  the  bottom  of  the  pitcher. 

The  whitish  maggots  riot  in  the  putrid  insect  remains, 
but,  of  the  dozen  or  so  that  there  are  to  start  with, '  usually 
but  one  matures,  even  when  there  appears  macerated  food 
enough  for  several '.  A  fratricidal  warfare  is  waged  which 
reduces  the  numbers  in  this  remarkable  way.  When  the 
survivor  has  attained  its  full  larval  size  it  bores  through  the 
leaf  and  burrows  in  the  ground.  After  a  few  days'  pupation 
it  issues  as  a  large  two-winged  fly.  Two  questions  natur- 
ally present  themselves,  Why  the  adult  escapes  the  fate  of 
all  but  one  of  the  other  insects  that  enter  or  tumble  into 
the  tube  ?  and  Why  the  maggot  is  not  killed  in  the  noxious 
fluid  in  which  it  revels  ? 

The  fly  is  probably  safe  because  it  has  strong,  spreading 
legs  with  large  adhesive  surfaces  and  strong  claws,  which 
enable  it  to  get  a  grip  of  the  cellular  tissue  of  the  pitcher 
surface  in  spite  of  the  slippery  downward-projecting  hairs. 
When  it  is  disturbed  within  the  pitcher  it  buzzes  about 
violently  and  emerges  in  most  cases  successfully.  It  is 
more  difficult  to  explain  the  survival  of  the  maggots,  ex- 
cept by  simply  pointing  to  other  cases  where  dipterous 
larvae  live  in  what  seem  to  be  hazardous  situations,  e.g. 
inside  the  food-canal  of  a  higher  animal  or  inside  decaying 
matter. 

The  other  intruder,  who  successfully  braves  the  dangers 
of  the  trap,  is  a  little  glossy  moth,  marked  with  grey-black 


THE  WEB  OF  LIFE  285 

and  straw-yellow.  This  Sarracenia  moth  (Xantkoptera 
semicrocea)  walks  with  impunity  on  the  treacherous  inner 
surface  of  the  pitcher  and  the  female  lays  her  eggs  singly 
near  the  mouth.  The  young  larva  spins  for  itself  a  carpet 
of  silk  and  draws  the  rim  of  the  pitcher  together  with 
a  web  which  shuts  out  all  other  insects.  It  works  its  way 
down  the  wall  of  the  pitcher,  devouring  the  cellular  tissue, 
and  dropping  large  quantities  of  undigested  food  into  the 
cavity.  It  is  a  half-looper  caterpillar,  with  beautiful  cross 
bands  of  white  and  purple  or  lake  red,  and  prominent  rows 
of  tubercles.  '  It  keeps  up,  in  travelling,  a  constant,  rest- 
less, waving  motion  of  the  head  and  thoracic  joints,  recall- 
ing paralysis  agitans.  The  chrysalis  is  formed  in  a  slight 
cocoon,  usually  just  above  or  within  the  packed  ex- 
crementitious  material.  There  are  two  broods  in  the 
year '. 

Here  we  have  two  good  examples  of  strange  habitat 
and  strange  mode  of  life.  The  flesh-fly  is  '  a  mere  intruder, 
the  larva  sponging  on  and  sharing  the  food  obtained  by  the 
plant '.  The  moth  is  an  active  enemy  spoiling  the  Sarra- 
cenia trap. 

Ants  and  Plants. — The  associations  between  ants  and 
plants  show  various  degrees  of  intimacy.  Ridley  distin- 
guishes three  groups  :  (1)  The  ants  may  be  sheltered  within 
the  leaves  or  flowers,  within  hollow  stems  or  thorns,  and  so 
on,  without  deriving  any  food  from  the  plant  or  conferring 
any  benefit  on  it.  (2)  In  the  case  of  some  epiphytic  ferns 
and  orchids,  the  ants  that  shelter  about  the  base  of  the 
plant  bring  up  considerable  quantities  of  soil.  (3)  Much 
more  intimate,  however,  are  those  cases  where  the  ants  live 
in  hollow  stems,  branches,  or  spines,  and  while  feeding  on 
secretions  exuded  by  glands  of  the  plant,  give  this  benefit  in 


THE  WONDER  OF  LIFE 


FIG.  46. — Acacia  Twig  (Acacia  sphaerocephala), 
about  two-thirds  natural  size.  (After  Schimper.) 
1.  The  large  hollow  thorns  which  are  tenanted 
by  ants.  2.  An  entrance  bored  through  a 
thorn.  3.  Small  inflorescence.  4.  A  compound 
leaf  in  resting  position.  The  bodyguard  of 
ants  which  live  in  the  shelter  of  the  acacia  do  it 
no  harm.  On  the  contrary  they  ward  off  the 
attacks  of  the  formidable  leaf-cutter  ants. 


return  that 
they  form 
a  body- 
guard, 
warding  off 
the  attacks 
of  other 
insects. 

An  as- 
soci  a  t  i  o  n 
that  still 
requires  a 
good  deal 
of  clearing 
up  is  that 
between 
ants  and 
the  laby- 
rinthine 
stem- 
tubers  of 
My  r  me- 
codia  tuber- 
o  s  a  ,  a 
famous 
Java^n  e  s  e 
epiphyte. 
The  tuber 
has  many 
passages 
and  cav- 
erns, which 


THE  WEB   OF  LIFE  287 

are  tenanted  by  ants  (Iridomyrmex  myrmecodius}.  Beccari 
thought  that  the  ants  were  responsible  for  making  the  laby- 
rinth, but  Forbes  and  Treub  proved  that  there  could  be 
typical  labyrinths  in  the  entire  absence  of  ants.  It  seems 
certain,  indeed,  that  the  tuber  is  a  water-absorbing  and 
water-storing  organ,  very  useful  to  a  plant  which  lives  quite 
off  the  ground.  At  the  same  time  the  association  with  ants 
is  very  general.  Miehe  points  out  that  some  of  the  walls  of 
the  maze  are  smooth  and  light  brown,  while  others  are 
warty  and  dark  brown.  A  dark  fungus  grows  on  the  rough 
surfaces,  not  on  the  smooth.  The  ants  deposit  their 
excrement  on  the  rough  surfaces  ;  they  use  the  smooth- 
walled  chambers  as  nurseries.  It  is  probable,  Miehe  thinks, 
that  the  excrement  of  the  ants  is  utilized  by  the  plants  ; 
and  this,  if  the  case,  may  be  a  very  useful  arrangement  for 
an  epiphyte  living  off  the  ground.  The  ants  get  a  conveni- 
ent shelter.  They  do  not  seem  to  eat  anything  that  be- 
longs to  the  plant,  though  what  they  eat  is  unknown. 
Nor  do  we  know  whether  they  can  get  along  without  their 
maze. 

Epizoic  Associations. — Many  plants,  such  as  Lichens 
and  Orchids,  grow  upon  other  plants,  and  are  known  as 
epiphytic,  and  the  term  may  be  also  applied  to  animals 
which  are  practically  confined  to  certain  plants,  e.g.  various 
Hydrozoa  and  Polyzoa  on  seaweeds,  not  in  any  real  para- 
sitism, but  because  the  situation  suits  them  well.  Similarly, 
we  have  epizoic  plants  and  animals.  The  green  Alga  on 
the  Sloth's  hair  is  epizoic.  The  seaweed  on  the  limpet's 
back  is  epizoic.  We  do  not  know  that  there  is  any  value 
in  the  last  association,  though  with  some  slight  change  of 
conditions  it  might  readily  become  invested  with  such 
value.  In  the  same  way  there  are  many  examples  of 


288  THE  WONDER  OF  LIFE 


FIG.  47. — Epizoic  growth  of  hydroid  polyps — Hydractinia  (A),  on  shell  of 
whelk — Buccinum  (B),  which  is  tenanted  by  a  hermit-crab.  For- 
ceps of  hermit-crab  (c).  The  hydroid  colony  shows  division  of 
labour;  it  includes  nutritive,  reproductive,  and  other  types  of 
individual. 

epizoic  animals :  acorn-shells  on  bivalves  and  crabs, 
Serpulid  worms  on  shells,  Hydrozoa  and  Polyzoa  on  many 
kinds  of  marine  animals,  one  sponge  on  another  and  so  on. 
Weber  refers  to  the  fact  that  the  muddy  floor  of  the  Banda 
Sea  is  covered  for  miles  with  a  dense  network  of  a  large 
Foraminifer,  Rhizammina  algceformis,  and  that  this  serves 
as  a  suitable  substratum  for  a  large  number  of  sedentary 
animals,  which  could  not  otherwise  find  a  foothold  in  the 
soft  mud. 

Of  many  of  these  epizoic  marine  animals  it  must  simply 
be  said  that  they  grow  upon  other  marine  animals  just  as 
they  might  grow  on  any  other  object.  The  young  stages 
happened  to  land  there  and  found  the  substratum  suitable. 
This  must  be  true  of  the  acorn-shells  (Balanns),  false-oysters 
(Anomia),  serpulid  worms,  Polyzoa,  zoophytes,  and  the 
like  often  found  on  crabs,  which  do  not  seem  to  illus- 
trate more  than  fortuitous  epizoic  association.  But  some 


THE  WEB  OF  LIFE  289 

of  the  cases  are  difficult.  Thus  Dr.  W.  T.  Caiman  describes 
a  crab  from  Christmas  Island  which  had  a  hydroid  polyp, 
allied  to  Stylactis,  attached  like  a  tassel  at  the  '  knee ' 
of  each  of  its  legs.  All  but  two  of  the  polyps  were  symme- 
trically disposed  and  the  rootwork  (or  hydrorhiza)  followed 
the  grooves  on  the  carapace.  Moreover,  the  type  speci- 
mens of  the  species  of  crab  (Medceus  haswelli),  although 
coming  from  another  and  distant  locality,  were  found  to 
bear  similar  or  identical  hydroids. 

Prof.  Alcock  has  described  the  curious  association 
between  a  Hydroid  (Stylactis  minoi)  and  a  small  rock  perch 
(Minous  inermis) ;  but  even  more  remarkable  is  Prof. 
Willey's  case  of  barnacles  growing  on  a  sea-snake.  His 
figure,  almost  mediaeval  at  first  glance,  shows  a  bunch  of  two 
kinds  of  barnacles  (Lepas  anserifera  and  Conchoderma 
hunteri)  attached  to  the  end  of  an  Indian  Ocean  sea-snake 
(Hydrus  platurus).  The  barnacles  are  not  in  any  way  para- 
sitic, they  are  simply  epizoic  ;  the  free-swimming  young 
forms  happened  to  fix  themselves  to  the  snake  instead  of 
to  a  drifting  spar.  But  it  is  interesting  to  notice  that  their 
occurrence  on  snakes  has  been  repeatedly  recorded.  To 
the  snake,  one  would  think,  they  must  prove  themselves 
a  troublesome  incubus,  seriously  impeding  its  movements. 

Some  of  the  epizoic  associations  certainly  become  dan- 
gerous to  the  bearer.  Prof.  Charles  Chilton  describes  such 
a  case  in  the  crab  Paramithrax  longipes,  which  seems  to  be 
almost  invariably  accompanied  by  specimens  of  the  acorn- 
shell  Balanus  decorus,  growing  on  its  carapace  and  some- 
times becoming  so  large  and  numerous  that  they  exceed  in 
size  the  body  of  the  crab  itself.  The  association  was  prob- 
ably quite  unimportant  in  its  initial  stages,  but  gradually, 
as  the  cirripedes  grew,  they  must  have  become  inimical 

y 


2  go  THE  WONDER  OF  LIFE 

to  the  crab's  welfare.  It  is  understood,  of  course,  that  as 
long  as  the  crab  is  growing,  it  moults  periodically  and  gets 
rid  of  its  associates  in  casting  its  shell.  It  is  after  growth 
has  stopped  that  the  burden  tends  to  become  too  heavy  to 
be  borne. 

The  sucking  fish  Echeneis  illustrates  the  difficulty  of 
classification.  It  fastens  itself  temporarily  to  other  fishes, 
to  turtles,  and  even  Cetaceans,  but  uses  them  simply  as  a 
means  of  transport.  It  is  no  more  a  parasite  than  a  man 
on  horseback. 

Shelter  Associations. — No  hard  and  fast  lines  can  be 
drawn,  but  it  seems  useful  to  group  together  as  '  shelter 
associations  '  a  number  of  interesting  cases  in  which  one 
animal  finds  shelter  in  or  about  another,  without  itself 
conferring  any  benefit  in  return. 

Fierasfer  is  one  of  the  best  examples  of  shelter-associa- 
tion. It  goes  in  and  out  of  sea-cucumbers,  starfishes, 
and  big  bivalves,  but  it  feeds  independently  like  any  other 
fish.  The  fact  is  that  it  belongs  to  a  family  (Ophidiidae) 
of  light-avoiding  fishes,  such  as  the  sand-eel  Ammodytes, 
and  yet  is  very  dependent  on  the  freshness  of  the  water. 
Thus  it  occurs  in  the  shelter  of  animals  in  which  there  are 
active  currents  of  water. 

The  entrance  of  Fierasfer  into  its  sea-cucumber  host 
has  been  described  by  Linton.  Apparently  by  accident 
the  fish  touches  the  body  of  the  sea-cucumber  (in  this  case 
Stichopus  moebii),  with  its  snout ;  it  at  once  feels  its  way 
backward  to  the  posterior  end  without  any  pause,  as  if  it 
was  following  a  scent ;  vision  does  not  seem  to  count  for 
much.  When  it  touches  the  cloacal  opening  it  brings  its 
slender  tail  sharply  round  with  a  rapid  whip-like  movement 
and  thrusts  the  tip  in.  Up  to  this  point  the  fish  is  excited ; 


FIG.  48— Fierasfer  acus,  entering  and  leaving  Holothurians.    (/l//er  Emery.) 


THE  WEB   OF  LIFE  291 

it  now  insinuates  its  body  into  its  host  in  a  quiet  leisurely 
way.  When  the  Holothurian  is  placed  in  water  with 
insufficient  aeration,  the  fish  comes  out,  and  rises  to  the 
surface,  taking  in  gulps  of  air. 

Numerous  small  horse-mackerels  (Carangldse)  swim 
about  under  the  shelter  of  the  umbrella  of  large  jelly- 
fishes,  and  other  small  fishes  find  safety  among  the  very  long 
and  hair-like  spines  of  the  dark-coloured  rock-urchin 
(Diadema  saxatile).  Prof.  Weber  notes  that  as  many  as 
ten  specimens  of  a  pelagic  fish  (Nomeus  gronovii)  may  be 
found  in  the  shelter  of  the  tentacles  of  the  Portuguese 
Man-of-War  (Physalia).  There  is  a  fish  called  Amphiprion 
bicinctus,  which  lives  inside  a  large  sea-anemone  (Crambactis 
arabica),  and  Prof.  Plate  has  described  Apogonichthys 
strombi,  from  the  Bahamas,  which  spends  at  least  part 
of  its  time  in  the  mantle  cavity  of  large  specimens  of 
Strombus  gigas. 

It  must  be  confessed  that  the  hermit-crab  does  not  seem 
to  be  always  happy  in  its  choice  of  a  shelter.  Prof.  Chilton 
tells  how  Eupagurus  stewarti,  which  has  a  straight  abdo- 
men, inhabits  tubular  cavities  within  a  Millepore  or  a 
calcareous  Polyzoon.  The  cavities  may  be  due,  as  Prof. 
Benham  suggests,  to  the  decay  of  a  branch  of  seaweed 
around  which  the  Millepore  or  the  Polyzoon  grew.  But 
the  point  is  that  the  calcareous  shelter  may  be  much  larger 
than  the  hermit-crab,  and  must  be  very  heavy,  if  not  too 
heavy,  to  carry  about. 

An  intermediate  state  of  affairs  is  illustrated  when  two 
animals  share  the  same  dwelling  without  sharing  food. 
Thus  the  prairie-owl  lives  with  the  '  prairie-dog  '  in  North 
America,  and  another  species  of  owl  with  the  Viscachas 
in  South  America.  Perhaps  in  the  same  category  may  be 


292  THE   WONDER  OF  LIFE 

ranked  the  '  Inquiline  '  gall-insects,  which  are  not  them- 
selves gall-producers,  but  utilize  what  others  make. 

Another  half -and-bet ween  case  is  that  of  a  moth,  Galleria 
melonella,  whose  caterpillars  feed  entirely  on  beeswax. 
The  female  lays  her  eggs  on  pieces  of  wax  or  wood  within 
the  hive ;  the  minute  grub-like  caterpillars  emerge  in 
about  eight  days  and  make  themselves  a  shelter  of  silk 
which  protects  them  from  the  stings  of  the  bees.  They 
feed  chiefly  on  old  honeycomb.  As  they  grow  they  en- 
large their  shelter  into  a  gallery  which  opens  on  the  surface 
of  a  comb.  When  they  reach  their  limit  of  growth  they 
make  cocoons  on  the  wall  of  the  hive  near  the  entrance, 
and  pass  out  as  moths  in  a  fortnight  or  so. 

Commensalism. — This  term,  which  is  just  the  same 
as  companionship,  '  eating  at  the  same  table  ',  may  be  use- 
fully restricted  to  external  associations  which  are  beneficial 
on  one  side  at  least.  When  the  benefit  is  two-sided,  the 
term '  mutualism  '  or '  commensal  mutualism  '  may  be  used. 

Many  associations  remind  one  of  the  beggar  at  the  rich 
man's  gate — a  small  creature  living  on  the  crumbs  from 
its  larger  host's  table.  But  it  is  difficult  to  draw  the  line 
between  cases  where  the  benefit  is  all  on  one  side  and  those 
where  some  degree  of  reciprocity  obtains.  Thus  Miss 
Winifred  Coward  has  described  a  peculiar  little  hydroid, 
Ptilocodium  repens,  which  grows  among  the  polyps  of  a 
Pennatulid,  Ptilosarcus,  from  the  Timor  Sea.  The  two 
kinds  of  animals  live  literally  '  cheek  by  jowl ',  and  as  the 
hydroid  has  numerous  defensive  polyps,  out-numbering 
the  nutritive  ones  (which,  it  is  interesting  to  notice,  have 
degenerate  tentacles),  it  may  be  that  it  confers  some  pro- 
tective advantage  on  the  Pennatulid  on  whose  food-supply 
it  levies  toll. 


THE  WEB  OF  LIFE  293 

A  vivid  description  of  the  partnership  between  the  giant 
sea-anemone  and  the  '  painted  fish '  (Amphiprion)  is 
given  by  E.  J.  Banfield  in  his  delightful  book  My  Tropic 
Isle  (1910).  The  dainty  fish,  only  an  inch  and  a  half  long, 
is  '  resplendent  in  carmine,  with  a  broad  collar  and  waist- 
band of  silvery  lavender  (or  rather  silver  shot  with  laven- 
der) and  outlined  with  purple '.  On  the  least  alarm  the 
fish  '  retires  within  the  many  folds  of  its  host,  entirely 
disappearing,  presently  to  peep  out  again  shyly  at  the 
intruder.  It  is  almost  as  elusive  as  a  sunbeam,  and  most 
difficult  to  catch,  for  if  the  anemone  is  disturbed  it  contracts 
its  folds  and  shrinks  away,  offering  inviolable  sanctuary. 
If  the  fish  be  dissociated  from  its  host,  it  soon  dies.  It 
cannot  live  apart,  though  the  anemone,  as  far  as  can  be 
judged  from  outward  appearances,  endures  the  separa- 
tion without  a  pang  '.  What  the  fish  does  for  the  anemone 
is  uncertain — perhaps  it  attracts  small  food.  But  other 
anemones  greedily  seize  inquisitive  fishes. 

Many  crabs  and  hermit-crabs  form  an  external  partner- 
ship with  sea-anemones,  which  grow  on  the  carapace,  or 
sometimes  on  the  forceps,  or,  in  the  case  of  some  hermit- 
crabs,  on  the  borrowed  Gasteropod  shell.  The  benefit  is 
clearly  two-sided,  and  a  Crustacean  bereft  of  its  partner 
anemone  has  been  known  to  search  for  it  diligently.  A 
hermit-crab  shifting  from  its  Gasteropod  shell  to  a  larger 
one  has  been  seen  trying  to  flit  its  partner  as  well.  To 
the  Crustacean  the  benefit  is  that  the  sea-anemone  can 
sting,  and  that  it  also  serves  as  a  marking  cloak.  To  the 
anemone  there  is  the  advantage  of  transport  and  of  crumbs 
from  its  companion's  table.  Prof.  Weber  refers  to  cases 
like  the  crabs  Polydectus  and  Melia,  where  the  anemone 
is  carried  about  on  the  forceps  in  a  highly  aggressive 


294  THE  WONDER  OF  LIFE 

way — the  one  animal  literally  making  a  tool  of  the 
other  ! 

One  of  the  most  extraordinary  cases  of  commensalism 
is  that  described  by  Colonel  Alcock  as  established  between 
an  Indian  Ocean  hermit-crab,  Paguristes  typica,  and  a  sea- 
anemone  of  the  genus  Mamillifera.  The  sea-anemone 
settles  down  on  the  hinder  part  of  the  young  hermit-crab's 
tail,  and  the  two  animals  grow  up  together  in  a  most  inti- 
mate manner,  the  spreading  anemone  forming  '  a  blanket 
which  the  hermit- crab  can  either  draw  completely  forward 
over  its  head  or  throw  half-back  as  it  pleases  '. 

A  very  well-known  association  is  that  between  a  hermit- 
crab  and  a  bright  orange  sponge,  Suberites  domunculd; 
which  spreads  over  the  Gasteropod  shell  which  the  hermit- 
crab  has  borrowed.  The  sponge  is  unpalatable  to  many 
animals  ;  it  is  packed  with  strong  needles  of  flint ;  and 
it  has  a  pungent  odour.  For  these  reasons  it  must  be  of 
advantage  to  its  bearer,  which  it  also  very  effectively 
masks.  It  seems  to  dissolve  away  the  Gasteropod  shell, 
but  this  is  probably  no  disadvantage,  since  it  lightens  the 
burden  the  hermit-crab  has  to  carry.  When  the  sponge 
settles  down  on  the  shell  inhabited  by  a  hermit-crab  which 
has  not  reached  its  limit  of  growth,  it  will  of  course  be 
left  behind  when  the  Crustacean  flits.  It  is  quite  possible 
that  the  vacated  shell  with  its  associated  sponge  may  be 
picked  up  by  a  smaller  hermit-crab  in  search  of  a  new  shel- 
ter. The  same  sponge  also  grows  on  the  back  of  Dromia 
vulgaris,  a  common  crab,  and  some  experiments  made  at 
the  Naples  Zoological  Station  by  Signor  Polimanti  brought 
out  two  very  interesting  facts,  first,  that  the  crab  takes  the 
initiative  in  getting  the  sponge  on  to  its  back,  planting  it 
there  itself,  and  second,  that  the  sponge  really  affords  its 


THE  WEB   OF  LIFE 


295 


partner  an  effective  protection  against  the  appetite  of 
cuttlefishes.  It  is  a  fine  case  of  diamond  cut  diamond, 
the  thrust  and  parry  between  crab  and  cuttle. 

A  number  of  animals  which  clean  up  others  without  utiliz- 
ing any  living  material  should  be 
ranked  with  the  commensals,  not  with 
the  parasites.  This  is  true  of  many  of 
the  so-called  fish-lice  (Argulidse),  which 
are  scavengers  of  the  skin  of  carp  and 
other  fishes,  and  of  various  insects  and 
mites  (e.g.  Trichodectes,  Philopterus), 
which  do  the  same  for  mammals  and 
birds.  Another  example  is  the  plover, 
which  Herodotus  accurately  described 
as  cleaning  the  mouth  of  the  crocodile, 
removing  leeches  and  other  parasites 
from  the  huge  gape. 

Symbiosis. — It  seems  to  us  justi- 
fiable and  useful  to  restrict  this  term 
to  the  mutually  beneficial  internal 
partnership  of  two  organisms  of  differ- 
ent kinds. 

In  most  Eadiolarians — pelagic  Pro- 
tozoa usually  with  siliceous  skeletons 
— there  are  symbiotic  Algae  which 
used  to  be  known  as  '  yellow  cells '. 
They  are  unicellular  plants  embedded 
in  the  transparent  living  matter  of 
the  Radiolarians,  and  a  very  profitable 
partnership  has  been  established. 
Being  possessed  of  chlorophyll,  the  Algse 
can  utilize  the  carbonic  acid  formed 


FIG.  49. — A  colonial 
Radiolarian,  Col- 
lozoum  inerme. 
(After  Brandt.) 
The  small  spheres 
are  the  units 
composing  the 
colony  ;  each  is 
accompanied  by 
partner  Algae ;  all 
are  imbedded  in 
a  transparent 
matrix.  Greatly 
enlarged. 


296 


THE  WONDER  OF  LIFE 


by  the  Radiolarian,  and  are  able  to  build  up  carbon- 
compounds,  such  as  starch.  They  give  off  oxygen, 
which  is  of  course  profitable  for  the  animal,  and  they 
doubtless  utilize  nitrogenous  waste  products  made  by 

the  animal.  If 
things  are  not  going 
well,  it  is  always 
open  to  the  Radio- 
larian to  digest  its 
partners  !  The  huge 
numbers  of  Radio- 
larians  —  alike  of  in- 
dividuals and  of 
specie  s  —  seem  to 
indicate  that  the 
symbiosis  is  very 
profitable. 

The  symbiotic 
Algae  are  known  as 
Zooxanthellae,  and 
their  occurrence  has 

FIG.  50.—  The  Green  Hydra,  expanded  and  been  recorded  in  a 
contracted.  The  expanded  form  shows 
the  male  organs  or  testes  as  swellings 
near  the  base  of  the  tentacles  and  the 
ovary  as  a  swelling  near  the  attached 
base.  The  transparent  ectoderm  is 
seen  as  a  layer  surrounding  the  endoderm  they  are  very  abun- 
which  contains  the  green  elements,  "  . 

usually  regarded  as  symbiotic  Algse.       dant   and   quite   in- 

dispensable.       Prof. 

Keeble  has  shown  that  the  larvae  do  not  develop  unless 
they  are  infected,  and  that  an  adult  which  has  been 
driven  by  straitened  circumstances  to  absorb  its  partners 
can  be  re-infected  and  given  a  new  lease  of  life. 


variety     of    animals. 

J 
In       the      Planarian 

n  , 

worm       tonvoluta, 


THE  WEB  OF  LIFE  297 

Besides  the  Zooxanthellae  there  are  other  symbiotic 
forms,  e.g.  the  green  Zoochlorellse.  Their  occurrence  is 
known  in  Amoebae  (a  colony  of  Amoeba  viridis  nour- 
ished for  ten  years  without  food),  in  the  green  Hydra,  in 
the  green  freshwater  sponge,  in  some  sea-anemones,  and 
in  many  Alcyonarians.  They  are  usually  referred  to 
the  family  Palmellacese,  but  are  not  certainly  known  to 
live  apart  from  symbiosis. 

Lichens. — One  of  the  most  striking  instances  of  partner- 
ship is  that  illustrated  by  lichens,  which  Schwendener, 
Bornet  and  other  botanists  proved  to  be  compound 
plants.  Each  consists  of  the  branching  and  interlacing 
threads  of  a  Fungus,  enclosing  partner  Alga  cells.  The 
Fungus  fixes  the  plant,  absorbs  air,  water  and  salts,  pro- 
tects the  Alga  from  drought  and  injury,  and  forms  spores 
which  are  wafted  away  by  wind  and  water,  and  may  start 
new  lichens  if  they  find  their  proper  partners.  The  Alga 
uses  the  sunlight  to  build  up  carbon  compounds,  and  it 
joins  with  the  Fungus  in  forming  sexual  reproductive 
bodies.  By  taking  proper  precautions  the  Alga  can  be 
got  to  live  in  water  without  the  Fungus,  and  the  latter 
can  live  on  sugary  media  or  the  like  without  the  Alga. 

The  life  of  many  a  lichen  is  rather  more  complicated 
than  we  have  indicated.  Thus  in  many  of  those  that 
grow  on  trees  the  Fungoid  elements  absorb  decaying 
organic  matter ;  and  some  tropical  forms  are  actually 
parasitic,  absorbing  food  from  the  living  tissues  of  leaf 
and  stem.  In  some  cases  the  Fungus  seems  to  kill  its 
partners  and  absorb  them.  The  Algae  are  sometimes  so 
much  shut  in  from  light  and  air  that  it  is  difficult  to  believe 
that  they  can  do  much  in  the  way  of  photo-synthesis, 
and  there  is  strong  evidence  that  in  such  cases  the  Algae 


298  THE  WONDER  OF   LIFE 

are  able  to  feed  upon  oxalic  acid,  and  perhaps  other  organic 
acids,  produced  by  the  Fungus.  But  after  we  allow  for 
these  and  other  complications,  there  remains  no  doubt 
that  many  lichens  illustrate  a  very  effective  symbiosis 
or  mutually  beneficial  partnership  of  a  Fungus  and  an 
Alga. 

A  very  interesting  three-fold  association  has  been  in- 
vestigated by  Prof.  Bottomley.  Nitrogen-fixing  Bacteria 
(Azotobacter  and  Pseudomonas)  are  found  along  with  Blue- 
Green  Algae  (Nostoc  and  Anabcena)  in  the  thallus  of  the 
liverwort  Anthoceros  and  in  the  leaves  of  Azolla,  the  Water 
Fern.  The  same  combination  of  Bacteria  and  Algae  is 
found  in  the  roots  of  Cycas.  It  may  be  that  the  Alga 
supplies  the  necessary  carbohydrate  for  the  Bacteria, 
and  that  the  host-plant  profits  by  the  nitrogen-fixing 
powers  of  the  Bacteria. 

It  is  usual  to  find  numerous  Bacteria  living  in  close 
association  with  animals — in  the  food-canal,  in  the  mouth, 
in  the  lungs,  in  the  tissues,  and  some  experts  have  raised 
the  question  whether  a  higher  animal  could  live  a  normal 
life  without  its  internal  flora.  By  ingenious  carefulness 
M.  Michel  Cohendy,  working  at  the  Pasteur  Institute, 
has  been  able  to  rear  chicks  to  an  age  of  forty-five  days 
without  their  showing  any  trace  of  microbes.  At  that 
date  they  became  too  big  for  their  antiseptic  cage  and  had 
to  be  let  out — quite  healthy  and  vigorous.  In  about 
twenty-four  hours  those  that  were  tested  had  the  usual 
stock  of  microbes.  As  they  stood  the  sudden  infection 
quite  well,  it  is  plain  that  the  power  of  resistance  to  ordinary 
microbes  is  inborn  or  constitutional,  not  an  individual 
acquisition. 

Just  as  there  are  friendly  Bacteria  in  many  animals, 


THE  WEB   OF  LIFE  299 

which  seem  to  help  to  oil  the  wheels,  so  yeasts  may  also 
be  co-operative.  An  instance  is  given  by  Dr.  Karel  Sulc, 
who  found  various  yeasts  of  the  Saccharomyces  (ordinary 
yeast)  type  living  inside  the  accumulated  reserve  material 
of  Aphides,  Scale-insects,  Cochineal  insects,  and  the  like. 
There  is  evidence  that  they  are  not  passive  inclusions,  but 
that  they  work  out  changes  in  the  stores. 

In  the  interesting  caterpillar  of  Nonagria  typhce,  which 
feeds  inside  the  stem  of  bulrushes,  the  digestive  area  is  very 
restricted,  and  Portier  could  find  no  evidence  of  a  ferment 
able  to  digest  cellulose.  But  there  were  present  in  great 
abundance  very  minute  organisms,  which  he  calls  '  pseudo- 
bacteria  ',  probably  of  the  nature  of  moulds,  which  work 
at  the  vegetable  tissue  and  break  it  down.  They  pass 
through  the  wall  of  the  intestine  and  are  engulfed  by  the 
caterpillar's  amoeboid  blood  corpuscles.  The  case  is  a 
very  extraordinary  one  and  must  be  re-investigated,  but 
it  looks  like  a  genuine  partnership,  as  if  the  '  pseudo- 
bacteria  '  were  middle-men  between  the  animal  and  its 
food.  We  are  reminded  of  the  beautiful  Infusorians  which 
seem  to  be  always  present  in  the  horse's  intestine,  helping 
in  the  breaking  down  of  the  hay  and  other  foodstuffs. 

The  microbe  (Pseudomonas  radicicola)  of  the  root-nodules 
of  Leguminous  plants  occurs  also  in  some  members  of 
other  orders.  Prof.  Bottomley  has  found  it  forming 
nodules  in  the  lateral  roots  of  the  bog-myrtle  (Myrica 
gale),  and  has  shown  that  young  plants,  grown  in  sterilized 
soil  poor  in  nitrogen,  do  not  flourish  unless  they  have  the 
root-nodules,  and  that  root-nodules  are  produced  on  unin- 
fected  plants  after  they  are  treated  with  a  culture  of  the 
microbe.  Miss  Spratt  has  also  found  the  same  form  in 
an  alder  (Alnus  incana)  and  in  two  buckthorns  (Elceagnus 


300  THE  WONDER  OF  LIFE 

edulis  and  Elceagnus  rhamnoides),  and  has  proved  its  bene- 
ficial nitrogen-fixing  role.  It  appears  that  the  microbes 
are  polymorphic,  rod-like  (bacillus)  forms  and  spherical 
(coccus)  forms  being  found  in  the  same  plant. 

Parasitism. — When  one  organism  lives  in  or  on  another 
— its  host,  gets  its  food  from  it,  is  inextricably  bound  up 
with  it  or  with  related  forms,  and  is  not  beneficial  but  rather 
injurious  in  its  influence,  we  speak  of  parasitism.  But, 
as  in  other  cases,  the  facts  are  too  subtle  for  absolutely 
precise  definition.  There  are  beautiful  Infusorians  in  the 
stomach  of  the  horse,  which  are  not  found  anywhere  else ; 
they  apparently  help  rather  than  hinder  the  process  of 
digestion  :  Are  they  symbions  or  parasites  ?  Many  small 
Crustaceans  are  found  on  the  skin  of  fishes,  where  they 
clean  up  mucus  and  the  like ;  it  is  hard  to  draw  the  line 
between  some  of  them  and  the  barnacles  on  a  whale's 
skin,  which  are  merely  epizoic.  Not  a  few  of  the  skin 
parasites,  e.g.  mites,  are  doing  their  best  to  clean  their 
host.  Many  parasites  seem  to  do  no  harm  to  their  hosts 
unless  these  get  out  of  condition  ;  this  is  probably  the  case 
with  many  of  the  threadworms  and  tapeworms  found  in 
the  food-canal  of  animals.  Some  parasites  are  quite 
unimportant  unless  they  get  shifted  into  peculiar  situations, 
such  as  the  vermiform  appendix  in  man,  within  which 
Nematode  worms  often  provoke  inflammation,  or  unless 
they  become  suddenly  very  numerous.  It  need  hardly 
be  said  that  the  definition  of  parasitism  must  be  such  as  to 
exclude  the  antenatal  life  of  the  young  mammal  within 
its  mother,  for  here  the  two  creatures  are  of  the  same 
flesh  and  blood,  and  though  the  benefit  is  onesided  and  a 
drain  on  the  mother,  she  is  adapted  to  her  offspring  as  no 
host  ever  is  to  its  parasite. 


THE  WEB   OF  LIFE  301 

Looked  at  broadly,  parasitism  is  a  way  out  of  the  struggle 
for  existence.  Just  as  some  animals  have  betaken  them- 
selves underground  or  into  caves  or  down  to  the  great 
abysses,  so  others  have  become  parasitic.  It  implies  an 
abandonment  of  direct  competition,  and  its  occurrence  at 
almost  every  level  among  backboneless  animals  shows  that 
it  has  been  frequently  resorted  to,  and  with  great  success, 
in  many  cases,  as  regards  self-preservation  and  increase 
in  numbers.  It  should  be  noted  that  in  many  parasitic 
types,  e.g.  among  Crustaceans  and  Insects,  only  the  females 
have  adopted  the  habit,  doubtless  in  relation  to  egg-laying 
and  the  protection  of  the  offspring. 

A  thoroughgoing  parasite,  such  as  a  tapeworm,  is  very 
effectively  adapted  to  the  conditions  of  its  life.  It  is 
safe  from  all  enemies  (unless  perhaps  the  practitioner  with 
his  vermifuge) ;  it  floats  in  a  plethora  of  food,  which  it 
can  absorb  by  the  whole  surface  of  its  tape-like  body ;  it 
can  live  and  thrive  with  a  minimum  of  oxygen,  and  it  has  a 
mysterious  '  anti-body '  which  preserves  it  from  being 
digested  by  its  host ;  it  has  muscular  adhesive  suckers 
and,  it  may  be,  attaching  hooks,  so  that  it  is  safely  fixed 
to  the  wall  of  the  intestine  ;  it  lives  in  warmth  and  comfort 
without  any  expensive  sense-organs  to  keep,  with  a  low  type 
of  nervous  system — a  life  of  dull  sentience.  It  has 
attained  to  what  economists  have  called  '  complete 
material  well-being '. 

The  other  side  of  it  is,  of  course,  degeneration.  The 
tapeworm  has  a  lowly  developed  nervous  system,  no  sense- 
organs,  slowly  contracting  smooth  muscles,  and  so  on. 
Only  its  reproductive  system  is  highly  developed,  and  even 
there  a  hint  of  degeneracy  may  be  found  in  the  self- 
fertilization  that  often  occurs.  For  some  of  the  tape- 


302  THE  WONDER  OF  LIFE 

worms  and  flukes  are  known  to  fertilize  their  own  eggs. 
External  parasites  are  naturally  much  less  degenerate  than 
internal  parasites ;  the  retrogression  is  proportionate  to 
the  thoroughness  of  the  parasitism. 

It  is  characteristic  of  parasites  to  be  prolific.  Some  of 
the  tapeworms  are  said  to  produce  eight  millions  of  eggs  ; 
the  female  Trichina  gives  birth  viviparously  to  fifteen 
hundred  young  ones  ;  a  liver-fluke  is  said  to  produce  some 
fifty  thousand  eggs.  There  are  two  ways  of  looking  at  this 
prolific  productivity.  On  the  one  hand,  as  regards  the 
individual  organism,  it  is  living  without  much  exertion, 
with  abundance  of  stimulating  food  at  its  disposal.  It  is 
physiologically  in  a  position  to  be  prolific.  On  the  other 
hand,  as  regards  the  race,  there  can  be  no  doubt  that  the 
prolificness  is  adaptive,  that  is  to  say,  those  types  of  parasite 
have  survived  which  were  constitutionally  prolific.  The 
risks  in  the  life  of  a  parasite  are  very  slight  when  it  is  en- 
sconced within  its  host,  but  they  are  often  enormous  in  the 
juvenile  stages,  or  when  there  is  transference  from  one  host 
to  another.  The  life-history  of  the  liver-fluke  and  the  ox- 
warble,  subsequently  referred  to,  may  be  taken  as  good 
instances  of  these  risks,  but  they  are  very  general. 
It  must  not  be  supposed  that  the  prolific  reproduction  was 
evolved  as  a  reponse  to  these  great  risks  ;  it  is  rather  to  be 
believed  that  those  parasites  which  were  constitutionally 
prolific  have  become  the  surviving  parasites.  There  are 
good  reasons  for  supposing  that  the  parasitic  alternative 
is  always  being  attempted  and  has  always  been  attempted, 
but  that  many  of  those  organisms  admitted  to  the  available 
asylums  have  died  out  within  them.  The  dog  is  known 
to  have  about  forty  different  parasites ;  both  man  and 
the  pig  have  more.  The  Scoter  duck  (CEdemia  nigra) 


THE  WEB   OF  LIFE  303 

harbours  sixteen  different  species  of  flukes.  Omnivorous 
animals  in  particular  are  peculiarly  liable  to  become  hosts 
of  alimentary  parasites.  It  is  well  known  that  oaks  are 
used  as  hosts  by  many  different  kinds  of  gall-flies.  In 
Europe,  Quercus  pedunculata  harbours  no  fewer  than  ninety- 
nine  different  kinds  of  gall-flies,  Q.  pubescens  seventy-nine, 
and  Q.  sessiliflora  ninety-six. 

Grouse  Disease. — Writing  in  1911  on  Grouse  Disease, 
Dr.  Arthur  Shipley  said  : 

'  Five  years  ago  we  knew  two  internal  parasites  (endo- 
parasites)  and  two  or  three  parasites  which  live  outside  the 
skin  (ectoparasites).  At  the  present  time  we  know  that 
grouse,  like  other  animals,  have  a  considerable  fauna  living 
both  in  and  on  them.  They  are,  in  fact,  not  only  birds,  but 
in  a  small  way  aviating  Zoological  Gardens.  The  scientific 
members  of  the  Grouse  Disease  Inquiry  have  recorded  eight 
different  species  of  insect  or  mite  living  either  amongst 
the  feathers  or  on  the  skin  of  the  bird  or  in  other  ways  closely 
associated  with  the  grouse,  and  no  fewer  than  fifteen  animal 
parasites  living  in  the  blood,  the  alimentary  canal,  the  lungs, 
or  other  organs.  Some  of  these  are  negligible.  They 
either  exist  in  too  small  numbers  or  infest  but  a  very  small 
percentage  of  the  birds  ;  others,  however,  are  found  in 
about  95  per  cent,  of  the  cases  investigated,  and  two 
at  least  are  associated  with  grave  disorders  which  often 
terminate  in  death '. 

One  of  these  is  a  Nematode  worm  (Trichostrongylus 
pergracilis),  of  which  there  may  be  10,000  in  one  grouse, 
about  equally  divided  between  the  two  intestinal  caeca, 
and  a  microscopic  Protozoon,  Eimeria  (Coccidium)  avium, 
which  lives  in  countless  numbers  in  the  delicate  lining 
membrane  of  the  food  canal  in  young  grouse. 


304  THE  WONDER  OF  LIFE 

The  almost  transparent  threadworm  (Trichostrongylus 
pergracilis)  of  the  grouse  spends  its  early  life  on  the  heather. 

'  The  eggs  give  rise  to  larvae  in  about  two  days.  The 
larvae  surround  themselves  about  the  eighth  day  with  a 
capsule  or  cyst  and  undergo  a  "  rest  cure."  After  a  period 
of  quiescence  they  quickly  change  into  second  and  active 
larval  forms,  which  are  minute,  transparent,  and  quite 
invisible.  These  lead  a  perfectly  free  life,  and  in  wet  weather 
gradually  squirm  and  crawl  up  among  the  leaves  and 
flowers  of  the  heather,  where  they  remain  until  swallowed 
by  the  grouse.  When  once  inside  the  bird,  the  larvae  make 
their  way  along  the  alimentary  track,  and  enter  the  caeca, 
where  they  rapidly  develop  into  adults '. 

There  are  some  parasites,  such  as  the  Liver  Fluke  and 
Trichina,  which  occur  in  numerous  hosts,  but  this  is  the 
exception.  The  rule  is  that  a  particular  parasite  occurs 
only  in  a  few,  usually  related,  forms ;  and  there  are  many 
parasites  which  occur  only  in  one  host,  or  only  in  two — 
one  for  the  young  asexual  stage,  and  the  other  for  the  adult 
sexual  stage.  The  reason  for  this  restriction  to  particular 
hosts  is  that  one  and  the  same  animal  is  not  likely  to  be 
adapted  to  a  variety  of  somewhat  subtle  environments. 
Moreover,  where  there  are  two  hosts,  the  adult  parasite 
can  only  occur  in  a  host  that  comes  into  very  close  vital 
relations  with  the  host  of  the  young  stages  of  the  said 
parasite.  Thus  the  bladderworm  of  the  rabbit  becomes 
a  tapeworm  in  the  dog  that  eats  the  rabbit ;  the  bladder- 
worm  of  pig's  flesh  becomes  a  tapeworm  in  man.  A  vivid 
instance  of  the  narrow  range  of  adaptability  in  some  cases 
may  be  inferred  from  the  fact  that  the  larva  of  the  liver- 
fluke  cannot  continue  its  life  in  Britain  except  within  the 
particular  species  of  water- snail  called  Lymnceus  trun-< 


THE  WEB  OF  LIFE  305 

catulus  or  minutus ;  if  it  enters  another  species  it  is  un- 
successful. Yet  the  same  larva  in  some  other  countries 
is  able  to  continue  its  life  in  other  species  of  water- snail ! 

When  an  examination  is  made  of  the  food- canal  of  a 
bird  or  mammal  or  other  Vertebrate,  which  has  not  been 
previously  studied,  some  new  species  of  parasite  is  very 
generally  found.  There  is  a  remarkable  individuality  in 
the  parasitic  infection  of  distinct  types.  This  probably 
illustrates  the  role  of  isolation  in  assisting  the  formation  of 
species.  Just  as  there  is  an  Orkney  vole  and  a  St.  Kilda 
wren,  and  a  distinct  species  of  snail  in  each  valley  in  Hawaii, 
so  there  are  different  tapeworms,  flukes  and  threadworms 
in  diverse  hosts.  In  some  cases,  where  the  species  of  host 
are  nearly  related,  the  species  of  parasites  seem  also  closely 
akin,  and  it  should  be  asked  in  such  cases  whether  the 
observed  differences  in  the  parasites  are  really  fixed  hered- 
itary characters,  and  not  individually  acquired  features 
induced  by  the  slight  peculiarities  of  environment. 

There  are  curious  little  Crustaceans,  called  Lamippids, 
of  the  order  of  Copepods,  which  occur,  for  instance,  in 
burrows  among  the  spicules  of  Alcyonarian  corals.  They 
are  very  distinctive  little  creatures,  characteristic  in  their 
buccal  armature  at  one  end  and  in  their  caudal  fork  at 
the  other.  They  have  been  studied  systematically  by 
A.  de  Zulueta,  who  finds  that  each  species  of  Lamippe 
has  its  particular  host.  Some  hosts  may  harbour  two  or 
three  species,  but  no  species  occurs  on  two  hosts.  It  would 
be  interesting  to  transfer  some  young  Lamippids  from  their 
proper  host  to  another,  to  see  whether  some  of  the  alleged 
specific  differences  are  not  directly  due  to  the  immediate 
environment.  Some  of  the  species  may  be  what  we  venture 
to  call  '  modification  species  '. 

x 


306  THE  WONDER  OF  LIFE 

Parasites  affect  their  hosts  in  a  great  variety  of  ways. 
Their  injurious  influence  may  be  trivial  or  serious,  direct 
or  indirect.  Skin  parasites  which  are  unimportant  may 
prepare  the  way  for  the  entrance  of  very  injurious  microbes. 
Intestinal  parasites  may  become  so  numerous  that  they 
interfere  with  the  host's  nutrition ;  several  hundreds  of 
large  threadworms  have  been  taken  out  of  a  horse's  stomach. 
They  may  cause  very  serious  perforations  of  the  wall  of 
the  intestine.  In  the  well-known  sturdie-worm  of  the 
sheep,  the  large  bladderworm  is  found  in  the  brain  or  in 
the  spinal  cord,  and  causes  disastrous  locomotor  disorders, 
and  often  death.  On  the  whole,  however,  the  relation 
between  parasite  and  host  is  remarkably  unimportant, 
partly  because  of  the  adaptability  of  the  organism,  and 
partly  because  the  very  aggressive  parasites  have  probably 
eliminated  themselves  from  time  to  time  by  killing  their 
hosts.  Such  a  case  as  Ichneumon  larvae  and  caterpillars, 
referred  to  elsewhere,  is  only  possible  because  the  insect 
larvse  pass  into  a  new  phase  of  life  after  they  have  killed 
their  hosts.  The  disastrous  effects  of  parasites  are  usually 
the  results  of  the  infection  of  new  hosts  who  have  not  become 
adapted  to  withstand  the  toxic  and  other  deleterious 
influences  of  the  intruders. 

Of  great  interest  are  those  cases  first  rightly  interpreted 
by  Professor  Giard,  where  the  parasite  destroys  the  repro- 
ductive organs  of  its  host,  effecting  '  parasitic  castration  '. 
Thus  male  crabs  infected  with  the  peculiar  crustacean 
parasite  called  Sacculina  have  their  whole  constitution 
profoundly  altered.  The  reproductive  organ  may  be 
destroyed  and  a  small  ovary — producing  ova — may  take 
its  place ;  the  shape  of  the  abdomen  approximates  to 
that  of  the  female  ;  and  the  protruding  parasite  is  actually 


THE  WEB   OF  LIFE  307 

guarded  by  its  bearer  as  if  it  were  a  bunch  of  eggs.  But 
we  cannot  do  more  than  give  a  glimpse  of  this  wonder  of 
parasitism. 

IN  ILLUSTRATION 

Liver -Fluke. — The  well-known  life-history  of  the  liver- 
fluke  (Distomum  hepaticum)  affords  vivid  illustration  of  the 
vicissitudes  that  are  so  common — especially,  it  may  be 
noticed,  in  the  case  of  parasitic  animals.  The  adult  lies, 
like  a  flat  leaf,  in  the  tributaries  of  the  bile-duct  of  the 
sheep  (and  some  other  mammals),  causing  the  disease 
known  as  liver-rot,  which  often  does  much  damage  among 
sheep.  Like  most  internal  parasites,  it  is  very  prolific, 
and  it  is  peculiar  inasmuch  as  it  fertilizes  its  own  eggs. 
The  developing  eggs  pass  down  the  bile-duct,  down  the 
intestine,  and  on  to  the  ground.  If  they  are  deposited  on 
quite  dry  ground,  they  soon  die  ;  if  they  come  to  rest  on 
damp  soil  or  among  wet  grass,  they  may  remain  in  a  state 
of  latent  life  for  a  couple  of  weeks  ;  if  they  fall  into  a 
pool  of  water,  they  continue  developing.  In  a  short  time 
there  emerges  out  of  the  egg-envelope  a  microscopic,  some- 
what pear-shaped,  ciliated  larva,  which  swims  freely  in  the 
water.  It  has  energy  to  continue  swimming  for  about 
eight  hours,  but  has  no  mouth  or  means  of  feeding.  In 
the  course  of  its  swimming  it  comes  into  contact  with 
many  things,  such  as  stick  and  stone,  water-weeds  and 
small  animals,  but  it  pays  no  heed  to  any  until  it  happens 
to  touch  the  little  water-snail  (Lymnceus  truncatulus  or 
minutus)  into  which  it  immediately  enters,  finding  the 
breathing  aperture  a  convenient  door.  If  we  could 
understand  the  memory  of  the  living  matter  which  enables 
this  tiny  brainless  larva  to  respond  effectively  to  the  touch 


30  8 


THE  WONDER  OF  LIFE 


of  the  only  creature  by  which  its  development  can  be  con- 
tinued, we  should  have  read  a  great  part  of  the  riddle  of 
life.  Inside  the  water-snail,  the  larva  loses  its  cilia  and 
two  eye-spots  which  it  had  ;  it  becomes  a  sporocyst  which 
falls  victim  to  precocious  asexual  reproduction  and  forms 
redise  ;  the  rediae,  which  are  larvae  of  a  second  type  with 
a  food-canal  and  other  complications,  usually  give  rise 


FIG.  51. — Three  stages  in  the  life-history  of  the  liver-fluke  (Distomum 
hepaticum).  I.  The  ciliated  free-swimming  larva,  with  cilia  (c), 
and  eye-spots  (E).  II.  The  sporocyst  stage,  showing  the  internal 
asexual  production  of  another  kind  of  larva — the  redia  (R).  III. 
The  last  larval  stage,  the  cercaria,  or  young  fluke,  showing  tail  (T), 
cyst-making  cells  (cc),  and  the  mouth  (M).  (After  Thomas.) 

to  more  redise ;  these  in  their  turn  produce — again 
asexually — a  third  type  of  larva,  known  as  the  cercaria, 
which  has  a  bilobed  food-canal,  the  beginnings  of  suckers 
and  gonads,  and  a  locomotor  tail.  The  cercarise  leave 


THE  WEB   OF  LIFE  309 

the  moribund  snail,  leave  the  water,  wriggle  up  blades  of 
grass,  and  encyst  themselves,  losing  their  tails  in  the  process. 
If  a  sheep  pass  that  way  and  eat  the  blade  of  grass  on 
which  the  cercaria  is  encysted,  the  life- history  is  continued, 
and  it  cannot  be  continued  in  any  other  way  !  From  the 
food-canal  of  the  sheep  the  cercaria,  now  a  young  fluke, 
migrates  up  the  bile-duct  to  the  liver,  and  there,  in  the 
course  of  a  few  weeks,  becomes  mature.  In  some  cases  the 
adult  liver-flukes  die  in  the  liver  after  they  have  repro- 
duced ;  in  other  cases  they  migrate  out  of  the  liver,  are 
passed  down  the  gut,  and  die  on  the  ground.  It  will  be 
noted  that  in  this  extraordinary  life-history  there  is  point 
after  point  at  which  the  process  may  come  to  an  end.  The 
eggs  may  light  on  dry  ground  ;  they  may  develop  in  a  pool 
without  water-snails  ;  they  may  exhaust  themselves  before 
they  come  across  the  water- snail ;  the  water-snail  con- 
taining them  may  be  swallowed  by  a  water- wagtail ;  the 
sun  may  dry  up  the  encysted  cercaria  ;  or  it  may  be  that 
no  sheep  comes  that  way  to  eat  the  infected  grass.  The 
whole  life-history  is  a  passage  over  a  Mirza-bridge  with  an 
exaggerated  number  of  possibilities  of  failure.  Had  it 
not  been  for  their  prolific  multiplication,  the  race  of  liver- 
flukes  would  long  since  have  come  to  an  end. 

Sacculina. — The  adult  parasite  which  protrudes  on 
the  under  surface  of  the  abdomen  of  crabs,  is  a  somewhat 
bean-shaped  sac,  consisting  very  largely  of  a  brood-chamber 
distended  with  eggs.  The  central  mass  includes  a  nerve- 
ganglion,  a  cement  gland  which  secretes  the  egg- cases, 
and  the  hermaphrodite  reproductive  organs.  There  is  no 
trace  of  digestive  or  circulatory  organs,  but  the  stalk  of 
the  parasite  is  continued  into  the  crab  and  divides  into 
numerous  '  roots ',  by  which  food  is  absorbed  and  waste 


3io  THE  WONDER  OF  LIFE 

excreted.  The  animal  is  at  the  nadir  of  parasitic  degener- 
ation. But  what  of  the  life-  history  ?  Out  of  the  brood- 
chamber  there  emerge  Nauplius-larvse,  with  three  pairs 
of  appendages,  a  food-canal,  and  a  median  eye.  They  feed 
and  grow  and  moult,  and  pass  into  a  second — the  Cyprid — 
larval  stage.  These  fix  themselves,  just  like  barnacles  and 
acorn-shells  (see  page  448),  by  means  of  their  first  pair  of 
feelers,  to  the  back  or  limbs  of  young  crabs,  finding  a  soft 
place  at  the  base  of  the  large  bristles  or  setae.  All  but 
the  head  region  is  cast  off  ;  the  structures  within  the  head 
contract ;  eyes,  tendons,  pigment,  and  the  remains  of  the 
shell  are  all  lost,  and  a  tiny  sac  sinks  into  the  interior  of 
the  crab.  Eventually  it  reaches  the  ventral  surface  of 
the  abdomen,  and,  as  it  approaches  maturity,  the  cuticle 
of  the  crab  softens  beneath  it,  so  that  the  sac-like  body 
protrudes.  It  seems  to  live  for  three  years,  during  which 
the  growth  of  the  crab  is  arrested.  The  reproductive 
organs  of  both  male  and  female  crabs  are  destroyed. 

Ox- Warbles. —What  an  extraordinary  story  is  that  of 
the  ox- warble  fly  (Hypoderma  bovis)  I  The  eggs  are  laid 
on  the  skin  and  are  licked  off  into  the  mouth.  According 
to  Jost,  they  hatch  at  the  foot  of  the  gullet,  and  the  larvaa 
bore  into  its  wall  and  wander  about  in  it  for  months  (July- 
November).  They  go  on  the  march  through  the  body, 
through  midriff,  connective-tissue,  kidneys,  and  what  not 
and  come  to  rest  beside  the  vertebrae  (December-May). 
Subsequently  they  pass  upwards  by  way  of  the  connective- 
tissue  of  the  back  muscle  to  a  position  just  below  the  skin 
of  the  back — the  last  chief  place  of  their  assembling.  They 
occur  here  from  January  till  July,  when  they  emerge  and 
fall  on  to  the  ground.  They  pass  into  the  pupa  stage  on 
the  ground  and  the  winged  fly  emerges  in  a  few  weeks. 


THE  WEB   OF  LIFE  311 

Some  of  the  tales  of  parasites  are  grim,  almost  like 
nightmare  imaginings.  Roubaud  has  told  us,  for  instance,  of 
two  species  of  fly  (he  called  the  genus  Chceromyia)  which  live 
in  the  burrows  of  the  Cape  Ant- Eater  and  the  Wart-hog. 
The  adults  live  on  dung  and  love  darkness.  The  larvae 
lie  in  the  damp  ground,  able  to  endure  prolonged  fasting, 
biding  their  time.  They  are  attracted  to  the  warmth  of 
their  hosts  ;  they  emerge  from  the  earth  and  fix  themselves 
to  the  skin,  piercing  it  and  drawing  blood.  They  can 
ingest  three  times  their  weight  of  blood.  Roubaud  reared 
one  on  himself,  which  reminds  us  that  there  is  another 
fly  of  somewhat  similar  habit,  Auchmeromyia  luteola, 
whose  larvae  pierce  the  human  skin  and  suck  blood. 

Fabre  tells  us  of  a  pigmy  black  Chalcid  fly  which  follows 
the  giant  Cigale,  like  a  Nemesis,  as  she  lays  her  eggs  in  the 
twigs.  As  soon  as  the  Cigale  has  filled  one  chamber  and 
passed  on  to  the  next,  the  anonymous  Chalcid  deliberately 
inserts  her  alien  egg,  which  effectively  undoes  the  larger 
mother's  labours.  For  out  of  the  egg  comes  a  grub  which 
devours  the  Cigale's  eggs.  '  A  small,  quick- hatching  grub, 
richly  nourished  on  a  dozen  eggs,  will  replace  the  family 
of  the  Cigale '. 

How  curious,  too,  are  the  facts  of  hyper-parasitism,  where 
one  parasite  preys  on  another.  The  gall-fly  Charips 
victrix  seems  to  destroy  a  beneficial  Braconid  that  preys 
upon  plant-lice ;  another  gall-fly,  Coihonaspis  zig-zag, 
destroys  Phora  aeletice,  which  is  a  parasite  of  the  injurious 
cut-worm  of  the  cotton. 

A  complication  in  regard  to  the  theory  of  galls  has  arisen 
through  the  growth  of  scepticism  as  to  the  part  which  the 
so-called  gall-making  animals  play.  Most  galls  are  believed 
to  represent  the  plant's  reaction  to  the  secretions  of  the 


312  THE  WONDER  OF  LIFE 

larva  which  hatches  from  the  egg  deposited  by  the  gall- 
making  animal,  and  there  can  be  little  doubt  that  this  is 
a  true  interpretation  in  many  cases.  But  there  are  other 
galls  which  arise  apart  from  insects  and  mites  altogether, 
namely  fungus-made  galls,  and  it  is  a  suspicious  fact  that 
there  is  often  a  striking  structural  resemblance  between 
the  animal-made  gall  and  the  plant-made  gall.  Therefore, 
Jules  Cotte  and  others  have  suggested  the  theory  that  many 
so-called  animal-made  galls  are  due  to  moulds  or  bacteria 
or  other  fungi  introduced  by  the  animal.  The  insect  or 
mite  would  thus  be  important  not  so  much  in  itself,  but 
because  it  carried  a  vegetable  infection,  and,  as  a  matter 
of  fact,  many  so-called  animal  galls  are  demonstrably 
associated  with  fungoid  growths.  Besides  the  frequent 
resemblance  in  structure  between  animal-made  galls  and 
fungus-made  galls,  there  are  other  notable  facts  which 
Cotte  utilizes  in  his  argument.  Animals  far  apart  from 
one  another  are  sometimes  able  to  make  very  similar  galls  ; 
the  same  animal  may  produce  very  diverse  galls ;  an 
animal  which  causes  galls  at  one  place  or  at  one  season 
may  be  inoffensive  at  another ;  there  is  sometimes  a 
puzzling  disproportion  between  the  dimensions  of  the  gall 
and  the  number  of  its  alleged  producers ;  some  galls  con- 
tinue to  grow  after  the  animal  parasites  have  disappeared, 
and  others  are  formed  before  the  egg  of  the  parasites 
hatches.  In  any  case,  we  have  another  illustration  of 
complex  interlinking  of  organism  with  organism. 

Pearls  and  Parasites. — It  is  well  known  that  if  a 
foreign  body,  such  as  a  grain  of  sand,  gets  in  between  the 
shell  of  a  mollusc  and  the  underlying  skin  (or  mantle) 
which  lines  it  and  makes  it,  fine  layers  of  nacre  may  be 
deposited  around  the  intrusion  and  a  sort  of  pearl  formed. 


FlG.  52. — A  section  of  a  reddish-brown  pearl,  showing  the  nucleus 
of  organic  matter  (periostracum),  and  the  concentric  layers  of 
lime  in  prisms,  with  delicate  intervening  layers  of  periostracum. 
(After  Rubbell.) 


312 


TH1   WONDER  OF  LIFE 


larva  which  hfttvtw*. 
making  anima* 
a  true  interpre 
galls  which 
namely  fur 
there  is  ^"- 
the  anim»< 
Jules  i  -  •        * 


euabun 
}o  <ti3^B 


the  egg  deposited  by  the  gall- 
**.'<  tlwre  can  be  little  doubt  that  this  is 
many  cases.     But  there  are  other 
from  insects  and  mites  altogether, 
^ills,  and  it  is  a  suspicious  fact  that 
"-  ng  structural  resemblance  between 

aid  the  plant-made  gall.     Therefore, 
*   iCAiwrs  have  suggested  the  theory  that  many 
-v  ***<i«  galls  are  due  to  moulds  or  bacteria 
produced  by  the  animal.     The  insect  or 
•>•  *e  important  not  so  much  in  itself,  but 
•r.*&  a,  vegetable  infection,  and,  as  a  matter 
-wvcalled   animal   galls  are  demonstrably 
•-'°i(l  gBWrtfc*     Besides  the  frequent 
jtriif  .  'iij.de  galls  and 

gniworis  ,nsaq  nwoid-naibbai  £  io  noilDsz  A  —  ,S£  ^Ol 

brus  ,(mi}oe,iizonsq)  isUsm  oinBgio  }o 
o  ^aysf  gninaviaJni  alBoifsb  rffiw  .zmshq  ni  ami! 


.'.{  i;;uv  '.iffvivHT  vi  -  ;  an 

'.  w.1-^  g-kilK  at  tn>*  t>iaK!*  *M  at  one  season 
may  bo  mofioB«v<.»  «r  aooUiM  ;  t)M«t  M  sometimes  a 
puzzliug  d»pn>|v,"»aoi*  S«?fw*HB  cite  ctimcMions  of  the  gall 
and  the  number  of  ;u  *H<*««d  p«*d«c«r8  ;  some  galls  con- 
tin  tie  to  grow  *ft*r  the  ajtimtU  parasites  have  disappeared, 

,  ,,  <  t  before  the  egg  of  the  parasites 

hatches.  .  >•  another  illustration  of 

complex  }•  anina  with  organism. 

Pearls  and  .  1  il  known  that  if  a 

foreign  body,  such  aw  a  grain  of  swmd,  gets  in  between  the 
shell  of  a  mollusc  and  ih  ng  skin  (or  mantle) 

whicl.  'rs  °^  nacro  may  be 

deposited  arouc  ]  .  •  nd  a  sort  of  pearl  formed. 


THE  WEB  OF  LIFE  313 

But  these  are  not  '  fine  pearls '.  The  experiment  has 
often  been  made  of  boring  a  hole  through  the  shell  and 
inserting  a  minute  fragment  of  mother-of-pearl  between  the 
shell  and  the  mantle ;  this  makes  a  centre  for  pearl-form- 
ation, and  a  more  valuable  semi-artificial  pearl  results. 
Gradually  it  began  to  be  suspected  that  the  really  fine 
clear  pearls,  with  translucent  centres,  were  formed  around 
minute  intruding  parasites,  which  the  skin  of  the  mollusc 
imprisoned,  somewhat  in  the  same  way  as  the  oak  imprisons 
the  larva  of  a  gall- wasp  within  an  '  oak-apple '. 

In  1902  H.  Lyster  Jameson  showed  that  the  agent  in 
forming  the  pearls  in  the  common  Edible  Mussel  (Mytilus 
edulis)  is  the  larva  of  a  parasitic  Trematode,  which,  instead 
of  secreting  a  cyst  of  its  own,  as  is  usual  with  such  larvae, 
stimulates  the  mussel  to  form  around  it  a  sac  of  epidermal 
cells.  These  cells  possess  the  same  physiological  properties 
as  the  outer  shell- secreting  epidermis,  and  eventually,  on 
the  death  of  the  Trematode  larva,  secrete  conchiolin  and 
calcareous  salts,  which,  deposited  in  concentric  layers  around 
the  remains  of  the  worm,  become  the  pearl.  But  the  life- 
history  remains  obscure.  It  is  possible  that  the  early  stages 
of  the  Mytilus  parasites  live  in  the  cockle  (Cardium 
edule),  where  closely  related  forms  certainly  occur.  It  is 
possible  that  the  adult  form  of  the  Mytilus  parasite  is  to  be 
found  in  the  Scoter  Duck,  but  the  experiments  made  to 
test  this  have  not  yielded  any  conclusive  result. 

It  has  been  suggested  that  the  fine  pearls  of  the  Ceylon 
pearl-oyster  are  due  to  the  larvse  of  a  tapeworm,  Tetra- 
rhynchus  unionifactor,  but  the  searching  work  of  Lyster 
Jameson  does  not  confirm  this  conclusion.  There  is  no 
doubt  that  the  young  stages  of  this  tapeworm  occur  in 
the  pearl-oyster,  along  with  pearls,  but  it  does  not  follow 


314  THE   WONDER  OF  LIFE 

that  the  larvae  cause  the  pearls.  It  may  be  a  case  of  two 
parallel  diseases,  comparable  to  the  case  of  a  dog  infected 
simultaneously  with  tapeworms  and  mange.  Mr.  Jameson 
maintains  that  pearls  arise  round  nuclei  of  some  variety 
of  shell- substance  formed  when  the  normal  rhythm  of 
secretion  is  disturbed. 

A  very  careful  study  of  the  formation  of  pearls  has  been 
made  by  A.  Rubbell  in  the  case  of  a  freshwater  mussel 
Margaritana  margaritifera,  which  is  common,  for  instance, 
in  some  of  the  mountain  streams  of  Bavaria.  His  obser- 
vations are  quite  against  the  theory  that  pearls  are  sepulchres 
of  flukes  or  any  other  parasites.  He  finds  that  they  arise 
around  minute  particles  of  a  yellowish  substance,  which 
resembles  the  outermost  layer  of  the  shell  (the  periostracum). 
The  pearls  are  formed  in  closed,  single-layered  sacs  of 
epithelium,  which  are  constricted  off  from  the  external 
epithelium  of  the  mantle,  that  is  to  say,  the  fold  of  skin 
which  hangs  down  like  a  flap  on  each  side  of  the  bivalve, 
lining  and  making  the  shell.  Growth  takes  place  by  the 
deposition  of  layer  after  layer  around  the  yellowish  centre. 
The  coalescence  of  several  pearl  sacs  may  give  rise  to 
curious  compound  pearls.  What  are  called  '  shell-pearls ' 
begin  in  the  mantle  and  become  secondarily  attached  to 
the  shell ;  they  are  to  be  distinguished  from  shell-concre- 
tions which  are  formed  around  intruded  bodies,  and  do  not 
show  any  concentric  layering.  According  to  Rubbell,  the 
innermost,  or  mother-of-pearl  layer  of  the  shell,  is  divided, 
at  certain  places  at  least,  into  an  inner  and  an  outer  stratum 
by  a  clear  intermediate  layer,  which  is  also  seen  inside 
the  pearls. 

It  appears,  then,  that  there  are  pearls  and  pearls. 
Keeping  to  those  which  are  formed  in  '  pearl-sacs '  of  the 


FlG.  53. — Shell  of  Freshwater  Mussel  (Margaritana  margaritifera), 
showing  two  pearls  near  the  margin.     (After  Rubbell.) 


314  THE   WONDER  OF  LIFE 

that  tht-  larvije  cause  tt«  pearls.  It  may  be  a  case  of  two 
parallel  diseases,  r<-><ti}'-vftU«  to  the  case  of  a  dog  infected 
simultaneous]  v  •  »ruis  and  mange.  Mr.  Jameson 

maintains  tkat  t*?ar*s  :^~*r  round  nuclei  of  some  variety 
of  shell-substttJ^  fxUfciVi  when  the  normal  rhythm  of 
secretion  in  i:-rh.aH"i 

A  vorv  ««f  c%c  formation  of  pearls  has  been 

road*-  by  A..   R«i--bf*»i  tu  Uw?  «ase  of  a  freshwater  mussel 
;  which  is  common,  for  instance, 

i*wwtak&  Breams  of  Bavaria.     His  obser- 
*:  7  \-rhat  pearls  aresepulchres 

. .  He  finds  that  they  arise 

Distance,  which 

BlnB§iBM)  feeauM  irtwAtttf  lo  H9H8— .K'-.Oll 
nigism  9H*  I69n  ehsDq  owl  SnJwo^s    of 
1  he  external 

^Hu»4ij  'f  skin 

; ;      . 

entre. 
rise  to 
• 

begin  -ittached  to 

tiif  ;rom  shell-concre- 

tiomi  whi'  'led  bodies,  and  do  not 

show  any  <•<;.»  -ording  to  Rubbell,  the 

innermost,  or  -f.  the  shell,  is  divided, 

at  certain  plac^  r  and  an  outer  stratum 

by  a  dear  intermediate  layer,  which  is  also  seen  iiiaide 
the  pefftfei 

It  pearls  and   p 

Keeping 


THE  WEB   OF   LIFE  315 

mantle,  we  may  distinguish  (1)  those  formed  around  an 
extrinsic  solid  inorganic  nucleus  such  as  a  quartz  particle  ; 
(2)  those  formed  around  an  extrinsic  organic  nucleus,  such 
as  a  parasite,  an  ovum,  or  a  fragment  of  tissue ;  (3)  those 
formed  around  a  minute  centre  of  the  shell-forming 
organic  substance,  called  conchin.  Very  interesting  ex- 
periments have  been  made  by  Alverdes,  who  introduced 
fragments  of  tissue  into  the  mantle  or  skin  of  mussels 
and  found  that  they  were  surrounded  by  concentric  layers 
of  mother-of-pearl. 


DOMESTIC  COMPLICATIONS 

We  have  already  seen  that  in  some  cases  an  animal 
cannot  continue  its  kind  without  the  unconscious  assistance 
— we  can  hardly  say  co-operation — of  other  creatures. 
The  mussel  needs  the  minnow  and  the  bitterling  needs 
the  mussel.  But  it  seems  almost  necessary  to  separate 
off  from  such  cases,  where,  after  all,  parental  care  is  quite 
in  evidence,  such  remarkable  occurrences  as  the  cuckoo's 
habit  of  handing  over  the  responsibilities  of  nurture  to 
a  foster-parent.  There  is  no  more  extraordinary  story 
in  the  whole  range  of  Natural  History,  and  it  becomes 
more  wonderful  the  more  we  probe  into  its  details. 

Habits  of  the  Cuckoo. — As  Aristotle  knew  so  many 
years  ago,  the  European  Cuckoo  (Cuculus  canorus),  foists 
her  several  eggs,  at  intervals  of  a  few  days,  into  the 
nests  of  various  more  or  less  appropriate  birds.  These 
foster-parents,  unconscious  of  being  fooled,  or  indifferent 
to  such  considerations,  hatch  the  cuckoo's  egg  among 
their  own  and  feed  the  hungry  self-assertive  nestling 
at  the  expense  of  no  small  wear  and  tear,  and  at  the 


316  THE  WONDER  OF  LIFE 

expense  of  eggs  or  offspring  of  their  own,  which  the 
young  cuckoo  ejects  from  their  proper  cradle.  '  The 
price  of  rearing  every  cuckoo  is  the  total  and  invari- 
able destruction  of  the  offspring  of  the  dupe '.  The 
question  that  so  many  naturalists  have  asked  is,  '  Why 
doesn't  the  cuckoo  brood  '  ?  Darwin  accepted  the  answer 
that  the  parasitic  habit  was  an  adaptation  to  the  fact 
that  the  mother-cuckoo  lays  her  eggs,  not  daily  as  most 
birds  do,  but  at  intervals  of  two  or  three  days.  Since 
the  American  cuckoos,  which  build  their  own  nests  and 
rear  their  own  young,  have  the  same  peculiarity  of  inter- 
rupted egg-laying,  Darwin  had  further  to  suppose  that 
these  were  just  beginning  to  lose  their  nesting  instincts — 
a  view  which  the  careful  studies  of  Francis  H.  Herrick  do 
not  at  all  confirm. 

The  important  facts  in  regard  to  the  European  cuckoo 
must  first  be  recalled.  The  breeding  range  extends  over 
a  large  part  of  Europe  and  Asia.  In  the  autumn  migration, 
the  adults  leave  the  young  to  migrate  independently  at 
a  later  date.  The  familiar  Spring  call  is  made  by  the 
male ;  the  female's  note  is  quite  different,  '  suggest- 
ing the  sound  of  bubbling  water  '.  She  is  polyandrous,  for 
a  time  at  least,  there  being  five  or  more  males  to  every 
female.  Some  authorities  maintain  that  there  is  no  true 
pairing. 

It  seems  impossible  to  doubt  that  the  bird  used  to  build 
a  nest  and  brood  in  former  days,  but  there  is  no  certain 
case  of  brooding  cuckoos  (Cuculus  canorus).  Careful 
ornithologists  have  spoken  of  the  bird  scheming,  playing  a 
trick,  watching  the  result  of  smuggling  her  egg  into  the 
chosen  nest,  and  even  Baldamus  writes  :  '  The  female 
cuckoo,  with  or  without  a  male,  and  either  before  or  after 


THE   WEB   OF  LIFE  317 

union,  searches  for  nests  of  suitable  nurses,  and  when  found, 
watches  them  from  the  beginning  of  nest- building  day  by 
day,  in  order  to  choose  the  one  most  suitable  '.  As  Herrick 
rightly  points  out,  we  must  be  careful  in  reading  choice 
and  motive  into  the  bird's  behaviour.  On  the  other  hand, 
we  must  not  try  to  make  an  automaton  of  this  remarkable 
bird. 

The  eggs  of  the  cuckoo  are  relatively  very  small,  they 
have  thick  resistant  shells,  they  show  an  extraordinary 
variability  in  colouring,  ranging  from  blue  or  blue-green, 
through  speckled  blue,  brown,  mottled  or  marbled  brown 
and  gray  to  nearly  plain  white.  There  is  strong  evidence 
that  the  same  cuckoo,  for  a  season  if  not  for  life,  lays  the 
same  type  of  egg.  In  one  particular  good  instance,  among 
others,  in  the  fine  Fenton  collection  of  eggs  in  Aberdeen 
University,  eleven  cuckoo's  eggs  taken  in  close  proximity 
(from  five  different  kinds  of  nests)  are  indistinguishable. 
In  many  cases  the  cuckoo  places  her  egg  in  the  nest  of  a 
bird  with  eggs  similar  in  size  and  colour  to  her  own,  but 
in  many  cases  it  is  quite  otherwise. 

It  is  doubtful  whether  this  resemblance  of  the  cuckoo's 
egg  to  that  of  the  foster-parent  is  of  any  practical  value. 
Herrick  writes : — 

'  We  should  like  to  know  how  many  of  the  119  potential 
nurses  of  this  bird  would  reject  an  egg  of  similar  size, 
whatever  its  colour.  We  know  that  many  birds  will 
accept  anything,  especially  after  beginning  to  breed,  while 
others  will  not.  Some  will  try  to  incubate  stones  or  pota- 
toes. .  .  .  The  uniformly  speckled  eggs  of  the  cowbird 
(Molothrus  pecoria)  fare  only  too  well  when  contrasted 
with  the  snow-white  eggs  of  the  mourning  dove,  and 
the  nearly  white  eggs  of  vireos,  flycatchers,  goldfinches 
and  bluebirds.' 


3i8  THE  WONDER  OF  LIFE 

In  most  cases  the  mother-cuckoo  lays  her  egg  on  the 
ground,  then  takes  it  in  her  bill,  and  then  puts  it  as  quickly 
as  possible  in  a  suitable  nest.  Baldamus  and  others  have 
vouched  for  the  fact  that  the  bird  sometimes  lays  her  egg 
in  the  nest  while  sitting  on  the  nest-wall.  This  is  said 
to  occur  especially  in  the  case  of  open  and  not  too  fragile 
nests.  According  to  Baldamus  the  cuckoo  lays  five  or 
six  eggs  at  intervals  of  six  or  seven  days  ;  some  observers 
state  the  intervals  as  two  or  three  days.  There  is  probably 
a  good  deal  of  variability  in  this  regard,  just  as  in  the 
colour  of  the  eggs. 

The  entire  progeny  of  the  cuckoo-nurse  is  destroyed. 
According  to  Jenner,  Blackwall,  Durham  Weir  and  many 
others,  the  young  cuckoo  gets  the  egg  or  offspring  of  the 
foster-mother  on  to  its  broad  depressed  back,  and  climbing 
on  the  side  of  the  nest  ejects  the  rightful  tenant.  This 
effective  dog-in-the-mangerish  behaviour  is  probably, 
Herrick  thinks,  '  a  reflex  response  to  a  contact  stimulus 
of  a  disagreeable  kind '.  Blackwall  made  the  significant 
remark  :  '  I  observed  that  this  bird,  though  so  young, 
threw  itself  backwards  with  considerable  force  when  any- 
thing touched  it  unexpectedly  '.  It  has  a  convulsive  hitch- 
ing movement  of  legs  and  wings  and  body,  which  appears 
to  be  exhausting.  The  response  dies  away  when  the  bird  is 
ten  to  fourteen  days  old,  after  which  anything  is  tolerated 
in  the  nest. 

According  to  Baldamus  and  some  other  Continental 
observers,  the  mother-cuckoo,  who  may  be  accompanied 
by  a  male,  occasionally  removes  the  eggs  of  the  nurse  — 
which  is  the  more  remarkable  since  the  cuckoo  is  not  an 
egg-eater,  but  feeds  mainly  on  hairy  caterpillars  and  other 
insects.  Baldamus  also  states  that  in  nests  which  the 


THE  WEB   OF  LIFE  319 

mother- cuckoo  cannot  readily  reach  '  the  young  of  the 
nurse  sometimes  grow  up,  but  are  often  suffocated  or 
starved  out  by  the  young  cuckoo,  and  are  later  removed 
by  their  own  parents  for  the  sake  of  cleanliness '.  There 
is  no  doubt  at  all  as  to  the  accuracy  of  the  British 
observations  that  the  nestling  cuckoo  evicts  the  eggs  or 
young  of  its  foster -parent,  but  it  seems  that  the  evicting 
reaction  is  not  always  exhibited  or  is  not  always  effective. 

After  the  young  cuckoo  leaves  the  nest  and  has  learned 
to  fly,  it  is  still  attended  by  its  foster-parents,  who  continue 
to  offer  food  to  their  changeling.  It  could  not  be  more 
'  spoiled '  were  it  their  child.  Who  can  tell  the  inward 
spirit  of  the  young  cuckoo  ?  But  without  maintaining 
that  the  creature  is  at  all  deliberate  in  its  treatment  of 
the  rightful  tenants  of  the  nest,  we  cannot  agree  with 
those  who  write  as  if  mental  disposition  were  a  negligible 
quantity.  It  has  its  fears,  for  instance,  but  how  charac- 
teristically it  '  expresses  its  fear  ',  as  Herrick  says,  '  in  a 
manner  calculated  to  inspire  fear  in  its  common  enemies  '. 
Jenner  observed  that  long  before  it  leaves  the  nest,  the 
irritated  bird  '  assumes  the  manner  of  a  bird  of  prey,  looks 
ferocious,  throws  itself  back,  and  pecks  at  anything  pre- 
sented to  it  with  great  vehemence,  often  at  the  same  time 
making  a  chuckling  more  like  a  young  hawk.  Sometimes, 
when  disturbed  in  a  small  degree,  it  makes  a  kind  of  hissing 
noise  accompanied  with  a  heaving  motion  of  the  whole 
body '.  In  the  American  black-billed  cuckoo  (Coccygus 
erythrophthalmus),  which  broods,  the  young  birds  give 
a  similar  expression  to  fear,  but  it  occurs  earlier  and  leads 
to  a  premature  desertion  of  the  nest — on  the  seventh  day  ! 

Some  light  on  the  problem  is  afforded,  as  Herrick  has 
shown,  by  a  study  of  the  American  cuckoo  (Coccygus 


320  THE  WONDER  OF  LIFE 

erythrophthalmics),  which  nests  and  broods.  It  also  has  a 
tendency  to  produce  eggs  at  irregular  intervals  (one  to  three 
days),  so  that  there  are  eggs  and  young  in  the  nest  for  a  longer 
time  than  usual.  Any  disadvantage  which  might  arise 
from  this  has  been  met  by  the  fact  that  the  young  ones 
leave  the  nest  in  succession  on  the  seventh  day  after  birth, 
and  thereafter  spend  a  couple  of  weeks  in  a  '  climbing 
stage  '  preparatory  for  flight.  In  this  climbing  the  young 
bird,  which  has  clambered  or  even  jumped  from  the  nest, 
moves  about  very  effectively  among  the  twigs.  It  grips 
the  twigs  very  firmly  with  its  feet  and  can  hang  head 
downwards  fastened  by  two  toes  !  '  It  profits  by  the 
strength  with  which  it  was  born  endowed,  and  the  exercise 
which  it  has  received  through  the  grasping  reflex,  for  it 
is  a  perfect  acrobat,  and  there  seems  to  be  no  necessary 
feat  of  climbing  of  which  it  is  incapable '.  Herrick  goes 
on  to  compare  it  to  the  young  of  the  old-fashioned  Hoatzin 
of  the  Amazons,  which  is  also  an  adept  climber  ;  both  use 
the  bill  to  help  the  toes,  but  the  Hoatzin  has  the  advantage 
of  having  a  clawed  thumb  and  first  finger. 

Now  the  interest  of  this  is  that  the  American  black- 
billed  cuckoo  shows  something  of  the  irregularity  in  egg- 
laying  which  the  European  cuckoo  shows,  and  that  it 
obviates  a  possible  disadvantage  by  the  peculiarity 
that  the  young  bird  leaves  the  nest  very  early,  and  has  a 
remarkable  climbing  period  during  which  it  has  a  strong 
sense  of  fear.  Prof.  Herrick  notes  two  other  points : 
'  When  disturbed  in  its  nest-activities,  the  black-bill  has 
been  known  to  transfer  its  eggs  to  a  new  nest  of  its  own, 
an  action  which  strongly  suggests  the  practice  of  the  Euro- 
pean cuckoo  of  carrying  its  laid  egg  to  the  nest  of  a  nurse.' 

'  The  American  species  occasionally  "  exchange  "  eggs, 


THE  WEB  OF  LIFE  321 

or  lay  in  other  birds'  nest,  and  when  so  doing  the  black- 
bill  has  been  known  to  struggle  for  possession  of  the  stolen 
nest '. 

Prof.  Herrick's  general  view  is  that  the  loss  of  the  nesting 
instinct  in  certain  cuckoos  and  cow-birds  is  due  to  an 
irregularity  in  the  rhythm  of  the  reproductive  cycle.  In 
most  birds  the  parental  instincts  or  the  cyclical  instincts 
connected  with  reproduction  follow  one  another  in  a  definite 
harmonious  series  '  with  almost  clock-Like  precision  ' — 
though  modifiable  at  every  point  by  intelligence. 

The  reproductive  cycle  is  made  up  of  a  series  of  acts 
or  chains  of  actions,  which  follow  in  a  definite  succession. 
Eight  or  more  terms  may  be  recognized,  but  the  classifica- 
tion is  unimportant,  so  long  as  it  is  observed  that  they 
are  serial  and  harmonious,  and  that  anything  which  pro- 
foundly disturbs  their  normal  attunement  is  disadvan- 
tageous, and  may  lead  to  disaster.  If  the  disturbance 
is  of  a  fundamental  and  permanent  character,  new  adjust- 
ments in  the  series  must  follow,  if  the  species  survive. 

The  cycle  may  be  graphically  represented  by  a  number 
of  nearly  tangent  circles,  each  of  which  stands  for  a  distinct 
sphere  of  influence  or  for  a  subordinate  series  of  related 
impulses  as  given  in  the  simplified  formula  : — 

1.  Migration ; 

2.  Mating ; 

3.  Nest-building ; 

4.  Egg-laying  in  nest ; 

5.  Incubation  and  care  of  eggs  ; 

6.  Care  of  young  in  nest ; 

7.  Care  and  '  education '  of  young  out  of  nest ; 

8.  Migration. 

One  term  in  the  series  may  be  weakened  or  drop  out ; 
another  may  be  exaggerated  and  prolonged ;  there  may 

Y 


322  THE  WONDER  OF  LIFE 

be  '  blending  '  and  '  overlap  '  of  instincts,  and  many  cases 
of  individual  disturbances  are  on  record.  A  bird  may 
build  a  new  nest  at  the  end  of  the  breeding  season ;  or 
it  may  build  a  supernumerary  nest ;  or  it  may  stop  nesting 
and  drop  the  eggs  on  the  ground ;  or  it  may  migrate  too 
soon,  leaving  its  young  to  perish.  The  most  common 
failure  is  in  the  adjustment  of  nest-building  to  the  time 
of  egg-laying,  and  at  this  point  '  parasitism '  arose.  The 
lack  of  attunement  between  egg-laying  and  nest-building 
is  casual  in  many  birds,  but  it  became  more  than  casual 
In  cuckoos  and  cow-birds.  A  modification  of  instincts 
ensued  and  a  modus  vivendi  was  arrived  at.  As  to  what 
started  the  lack  of  attunement,  we  can  only  say — '  a 
nervous  variation',  such  as  all  highly  strung  creatures 
frequently  exhibit. 

Jenner  pointed  out  that  the  bird  has  but  a  short  time 
to  stay  in  its  breeding  area,  and  much  to  do  in  that  short 
time.  The  gain  of  leaving  the  eggs  to  a  succession  of 
other  birds  is  manifest.  Other  naturalists  have  indicated 
various  advantages  which  make  it  easier  to  understand  the 
development  of  the  habit  by  selection,  but  leave  the  origin 
of  the  habit  obscure,  except  that  it  is  well  known  of  many 
birds  that  they  casually  lay  an  egg  in  another  bird's  nest. 

Many  years  ago  we  suggested,  like  Prof.  Eimer,  that  the 
peculiar  habit  should  be  considered  as  an  outcrop  of  a 
very  peculiar  constitution  and  character.  That  is  to  say, 
the  non-brooding  is  not  to  be  held  apart  from  many  other 
peculiarities  of  the  cuckoo  with  which  it  is  congruent.  We 
referred,  for  instance,  to  the  absence  of  any  *  married 
life  ',  to  the  preponderance  of  males,  to  the  polyandry  that 
obtains,  to  the  insatiable  and  gluttonous  appetite,  as  well 
as  to  the  sluggish  interrupted  egg-laying.  That  any 


THE  WEB   OF  LIFE  323 

peculiar  habit  should  be  considered,  not  by  itself,  but  in 
its  setting  along  with  the  whole  constitution  and  character 
seems  to  us  still  a  sound  proposition. 

In  spite  of  many  suggestions,  the  puzzle  of  the  peculiar 
habit  remains,  and  Baldamus,  who  devoted  his  whole  life 
to  cuckoos,  finished  up  his  big  monograph  with  the  dis- 
appointing words  :  '  All  answers  to  the  wider  questions 
of  how  and  why,  in  my  opinion,  can  be  based  only  on  con- 
jectures :  and,  however  clever  many  of  these  may  be,  for 
exact  science  they  have  scarcely  any  value  at  all '.  It 
cannot  be  said,  however,  that  this  is  true  of  the  careful 
study  of  the  behaviour  of  the  cuckoo  by  Prof.  Francis  H. 
Herrick,  of  Cleveland,  which  we  have  utilised  in  the 
foregoing  pages. 


ANIMAL  SOCIETIES 

Many  animals  form  coherent  colonies,  by  budding  or 
by  some  form  of  division,  the  whole  being  physically  con- 
tinuous. Every  grade  occurs  between  mere  aggregates, 
where  the  component  units  are  closely  juxtaposed  but 
not  intimately  inter-dependent,  as  we  see  in  many  corals, 
and  subtle  integrates  where  the  whole  colony  may  move 
and  behave  as  one  creature,  as  we  see  in  the  free-swimming 
Portuguese  Man-of-War  (Physalid)  or  in  the  Fire-Flame 
(Pyrosoma).  It  is  difficult  to  draw  the  line  logically,  but 
it  seems  clearer  to  keep  the  term  colonies  for  those  com- 
binations where  the  bond  of  union  is,  in  part  at  least, 
physical. 

Many  animals  live  together  in  companies,  but  without 
there  being  much  or  anything  in  the  way  of  a  corporate 


324  THE  WONDER  OF  LIFE 

life.  Great  numbers  of  sedentary  animals  may  live  beside 
one  another,  like  daffodils  by  the  lake  side.  Large  shoals 
of  herring,  mackerel  and  other  fishes  may  swim  about 
together,  and  it  is  rather  interesting  that  there  are  many 
different  names  for  the  various  crowds.  But  association 
in  numbers  is  not  sociality.  It  will  be  found  difficult, 
however,  to  draw  a  firm  line,  for  many  gregarious  animals 
act  together  on  occasions  or  may  exhibit  such  devices  as 
posting  sentinels.  There  we  see  the  first  hints  of  societary 
life. 

Crowds  without  Sociality. — The  fiddler-crabs  (species 
of  Gelasimus  or  Uca)  may  serve  as  an  illustration 
of  animals  living  together  in  great  numbers  without  there 
being  any  real  sociality.  They  swarm  on  the  mud-flats 
and  estuary-shores  near  Manila,  and  in  many  similar  places, 
— attractive  and  interesting  creatures.  One  of  the  great 
claws  of  the  male  is  enlarged  out  of  all  proportion,  and 
is  used  as  a  weapon.  According  to  Colonel  Alcock,  '  it 
is  used  as  a  signal  to  charm  and  allure  the  female ',  but 
this  view  is  not  confirmed  by  the  observations  of  Mr. 
A.  S.  Pearse  at  Manila.  The  males  certainly  dance  about 
the  females,  but  as  they  keep  their  backs  constantly  toward 
the  females  the  great  claw  could  not  be  seen.  It  is  not 
used  in  burrowing  or  feeding ;  in  fact  it  seems  rather  in 
the  way,  but  it  is  '  of  unquestionable  use  to  the  male  in 
his  combats  with  his  fellows  and  in  defending  himself 
from  other  enemies  '.  But  our  present  point  is  simply 
that,  although  the  fiddler-crabs  live  in  great  colonies, 
they  show  no  communal  life,  except  perhaps  a  certain 
playfulness.  They  are  fiercely  individualistic  and  very 
pugnacious.  They  make  burrows  and  carry  away  the 
excavated  material ;  they  close  the  opening  with  a  plug 


THE  WEB   OF  LIFE  325 

of  mud  when  the  tide  comes  in ;  they  make  a  sort  of 
'  preserve '  of  a  circle,  of  a  yard  or  so  in  radius,  of  which 
the  burrow  is  the  centre.  '  Each  fiddler ',  Mr.  Pearse 
writes,  '  researches  the  mud  around  his  hole  for  food,  and 
his  hand  is  against  every  man.  He  is  ever  ready  to  dart 
into  his  burrow,  and  if  danger  threatens  he  quickly  retreats 
into  this  refuge.  If  one  of  his  fellows  approaches  too  close 
to  his  domain,  he  rushes  forth  and  enters  into  fierce  combat. 
Each  crab  makes  his  hole  the  centre  from  which  all  his 
activities  are  conducted,  and  he  treats  the  approach  of 
any  intruder  as  an  unfriendly  act '.  The  plugging  of  the 
burrow  when  the  tide  comes  in  serves  as  a  protection 
against  fishes  and  snakes  and  other  enemies  which  hunt 
at  the  edge  of  the  advancing  tide. 

Mr.  Pearse  points  out  that  several  circumstances  might 
be  held  as  favouring  the  development  of  some  social  life, 
but  it  is  evidently  not  consistent  with  the  Crustacean  con- 
stitution. The  mothers  carry  the  eggs  and  young  for  a 
time,  thus  having  opportunity  to  start  a  colony  with  them. 
The  aggressive  ways  of  the  males  might  enable  stronger 
individuals  to  gather  a  number  of  females  about  them, 
but  there  is  nothing  of  this  sort.  The  fiddlers  live  in 
enormous  colonies,  but  there  is  nothing  in  the  way  of 
combination  or  co-operation — rank  individualism  obtains 
throughout. 

The  distinctive  features  of  animal  societies  will  become 
clearer  as  we  consider  particular  illustrations  ;  it  is  enough 
at  the  outset  to  recognize  that  an  animal  society  is  not 
physically  continuous  like  a  colony,  and  that  it  is  more 
than  a  gregarious  association.  It  means  a  community 
of  separate  individuals  with  more  or  less  of  a  corporate 
life,  and  with  the  power  of  acting  as  a  unity. 


326 


THE  WONDER   OF  LIFE 


The  Ant -Hill. — When  we  look  at  an  ant-hill  with  its 
multitudes  and  their  industry — without  haste  and  without 
rest — we  feel  at  once  that  the  spectacle  before  us  is  very 
different  from  that  presented  by  the 
crowd  of  mites  in  an  old  cheese.  It  is 
not  a  mere  association  of  huge  numbers, 
it  is  a  community. 
..  Let  us  look  into  the 
matter  more  closely. 

The  ant  community 
shows  division  of 
labour.  Besides  the  queens  or  mothers 
and  the  males,  there  is,  as  every  one 
knows,  the  throng  of  workers — females 
by  nature,  who  do  not  normally 
become  reproductive.  There  is  often 
considerable  difference  in  structure 
between  queen,  male  and  worker  ;  and 
then  we  speak  of  polymorphism.  More- 
over, there  may  be  several  castes  of 
workers  discharging  different  tasks — 
foraging,  nursing,  fighting,  and  so  on. 
And  there  may  be  polymorphism 
among  the  workers.  Thus,  Bates 
described  among  the  leaf-cutting  ants, 
(1)  the  ordinary  workers  with  rela- 
tively small  heads,  (2)  officer-like 
individuals  with  large  bald  heads,  and 
(3)  another  type  with  a  twin  simple-eye 
in  the  middle  of  the  forehead — three 
forms  different  from  one  another  within 
one  species. 


FIG.  54.  —  Leaf-cut- 
ting ants  at  work, 
Atta  discigera.  A, 
an  ant  without  a 
burden ;  L,  an  ant 
with  a  leaf  ;  s,  an 
ant  with  a  piece 
of  stem.  (After 
Moeller.) 


THE  WEB  OF  LIFE  327 

Another  outstanding  feature  is  the  instinctive  socializa- 
tion. Put  it  as  one  may,  there  is  no  getting  round  the  big 
fact  that  these  ants  have  to  a  very  large  extent  given  up 
working  for  their  own  hand.  While  they  satisfy  their 
own  needs  by  the  way,  the  bulk  of  their  energy  is  expended 
pro  bono  publico,  for  although  we  may  not  be  justified  in 
saying  that  they  toil  and  moil  consciously  for  the  sake  of 
anything,  it  is  certainly  not  for  themselves  that  they  are 
so  indefatigable  and  persevering.  Noteworthy  is  the  fact 
that  in  some  ant-communities  it  seems  to  be  a  convention 
— an  unwritten  law — that  if  an  '  empty  '  ant  applies  to  a 
full  one  for  food,  he  must  forthwith  be  fed.  This  is  carrying 
out  the  idea  of  community  of  goods  to  its  utmost  limit. 

The  capacity  for  unified  action  is  well  illustrated  by 
the  battles  between  rival  ant-hills,  and  by  the  slave-making 
raids  in  which  the  pupae  of  another  species  are  captured 
and  brought  home  to  grow  up  into  servitude.  In  some 
cases  the  slave-keeping  has  gone  so  far  that  the  economic 
stability  of  the  community  depends  solely  on  the  enslaved 
species,  with  whom  the  fundamental  business  of  production 
rests.  The  final  result  may  be  that  the  *  masters '  seem 
to  become  enervated  and  unable  to  fend  for  themselves. 
In  the  well-known  instance  of  the  Amazon  ant,  Polyergus 
rufescens,  the  '  masters '  have  to  be  fed  by  the  '  slaves  '. 
Very  curious  also  is  the  fact  that  in  the  raids  the  old  slaves 
take  their  share  in  capturing  new  ones. 

Co-operation  in  dragging  a  burden  is  a  familiar  sight 
and  illustrates  the  socialization  of  the  ant.  But  there 
are  many  subtler  cases.  Prof.  Bugnion  of  Lausanne  has 
corroborated  many  of  the  older  observations  on  the  tailor 
ant,  (Ecophylla  smaragdina,  which  is  common  in  hot 
countries.  He  vouches  for  their  extraordinary  habit  of 


328  THE  WONDER  OF  LIFE 

using  their  silk-secreting  larvae  (they  have  no  silk  them- 
selves) as  needle  and  thread  when  they  are  binding  leaves 
together  to  make  a  nest.  We  have  here  an  anticipation 
of  the  child  labour  of  the  early  part  of  the  industrial  age  ! 

The  story  reads  like  a  burlesque,  and  it  surely  makes 
it  difficult  to  accept  the  opinion  of  some  naturalists 
that  instinctive  behaviour  is  unaccompanied  by  any 
awareness  of  meaning  or  feeling  of  the  end.  Whenever  this 
difficulty  is  obvious,  it  is  customary  to  say  that  intelligence 
has  for  the  time  being  taken  the  reins.  In  any  case,  the 
facts  are  wonderful  enough. 

An  eye-witness,  Mr.  L.  G.  Gilpin-Brown,  writes  from 
Ceylon  : — 

'  Sometimes  one  will  see  an  ant,  with  a  larva  in  its  man- 
dibles, stalking  aimlessly  about  on  the  outside  of  the  nest. 
It  stumbles  on  a  small  hole.  It  proceeds  to  study  that 
hole,  walks  all  round  it,  walks  over  it,  and  eventually 
decides  that  it  really  is  a  hole,  whereupon  it  proceeds 
to  business.  Feeling  round  the  edge  with  its  antennae 
it  dumps  the  head  of  the  larva  on  one  side  so  as  to  fasten 
the  thread  of  silk  there,  moves  over  and  fastens  it  down 
on  the  other  side,  comes  back  again,  and  so  on ;  each 
trip  leaving  a  thread  of  silk  behind,  until  the  hole  is  com- 
pletely sealed  up.' 

The  tailor  ants  nest  in  trees  and  they  sometimes  find  it 
difficult  to  bring  two  rather  distant  leaves  close  enough 
together  to  be  sown.  Then,  as  Bugnion  relates,  they  have 
recourse  to  a  perfectly  extraordinary  co-operation.  Five 
or  six  will  form  a  living  chain  to  bridge  the  gap.  The 
waist  of  A  is  gripped  in  the  mandibles  of  B,  who  is  in  turn 
gripped  by  C,  and  so  on — a  notable  gymnastic  feat.  Time 
does  not  appear  to  be  of  much  account,  but  they  work 


THE  WEB  OF  LIFE  329 

definitely  towards  a  result,  and  many  chains  may  work 
together  for  hours  on  end  trying  to  draw  two  leaves  close 
to  one  another.  We  could  not  have  a  better  instance  of 
social  co-operation. 

The  foundation  of  a  new  ant-colony  takes  place  in  various 
ways.  After  the  nuptial  flight  the  males  die,  and  the 
females  that  escape  the  numerous  pitfalls  take  refuge 
in  crevices  in  the  ground  and  lay  their  eggs.  Janet  has 
shown  that  the  muscles  of  flight  degenerate  and  break  up 
after  their  use  is  past,  and  it  seems  that  the  material  serves 
for  the  nutrition  of  the  mother  at  this  critical  time.  In 
Atta  sexdens  and  some  other  cases,  Pieron  points  out 
that  the  provident  female  carries  with  her  a  supply  of  the 
mycelium  of  an  edible  fungus  on  which  she  and  her  offspring 
afterwards  subsist.  When  the  earliest  workers  are  hatched 
it  may  be  necessary  to  sacrifice  some  of  the  eggs  to  keep 
things  agoing. 

Sometimes  the  fertile  female  utilizes  a  deserted  nest  of 
some  other  species,  or  sneaks  into  a  tenanted  nest.  Some- 
times the  home  of  a  small  species  is  as  it  were  grafted  on 
to  that  of  a  large  species,  which  it  plunders.  Sometimes 
the  fertile  female,  falling  near  her  old  home,  or  the  nest 
of  the  same  species,  is  joined  by  workers  who  help  her  to 
start  a  new  nest.  Sometimes  the  workers  of  another  species 
will  receive  a  fertile  female  into  the  nest,  with  the  result 
that  their  own  queen  abdicates,  or  is  killed,  or  shares  the 
honours  with  the  new-comer.  Very  curious  are  the  cases 
where  a  warlike  queen  enters  a  foreign  nest,  drives  off  the 
adult  tenants,  and  establishes  herself  as  foster-queen  of 
their  undeveloped  progeny. 

The  way  in  which  a  new  colony  is  started  has  a  good 
deal  to  do  with  the  economy  that  is  established.  It  may 


330  THE  WONDER  OF  LIFE 

be  quite  sufficient  in  itself — the  workers  discharging  all 
the  tasks  of  food-getting,  nursing,  building  and  fighting. 
When  a  mixed  nest  has  been  formed,  the  workers  may 
become  semi-parasitic  (as  in  the  small  Soknopsis),  or  may 
be  treated  as  the  guests  of  the  other  species.  This  leads 
on  to  slavery.  But  strangest  of  all  are  those  cases  where 
there  are  no  workers  at  all,  but  only  males  and  females. 
The  fertile  queen  may  be  received  into  a  foreign  nest, 
and  the  rightful  queen  may  be  killed  instead  of  the 
intruder.  But  this  means  sooner  or  later  the  end  of 
that  nest,  for  there  can  be  no  further  production  of 
workers. 

According  to  M.  Pieron  the  primitive  mode  of  nest- 
founding  is  that  in  which  the  female  is  able  to  do  it  all  by 
herself.  This  is  illustrated  by  Formica  fusca,  which  is 
probably  an  ancestral  species,  being  indistinguishable 
from  Formica  flori  of  the  Baltic  amber.  A  second  stage 
is  exhibited  in  Formica  rufa,  where  the  female  is  unable 
to  found  her  nest  unless  she  gets  help  from  friendly  workers 
either  of  her  own  or  of  some  different  species.  Then  follow, 
in  great  variety  of  detail,  the  various  stages  of  parasitism 
and  slavery. 

Among  the  many  remarkable  facts  concerned  with  the 
founding  of  a  new  colony,  let  us  call  attention  to  two  of 
the  strangest.  When  a  fertilized  queen  finds  a  suitable 
shelter  and  begins  to  lay,  she  often  has  to  eat  a  few  of  her 
own  eggs — to  keep  agoing.  The  others  hatch  into  workers, 
who  are  soon  able  to  help  the  mother.  But  more  eggs 
may  have  to  be  sacrificed.  If  the  female  falls  into  a  nest 
of  her  own  kind,  she  lays  her  eggs  there,  and  the  workers 
tend  the  larvae  carefully.  But  Miss  Adele  Fielde  has  shown 
that  if  the  tips  of  the  workers'  antennae  are  snipped  off  they 


THE   WEB   OF   LIFE  331 

do  not  look  after  the  larvae  !  They  require  some  gustatory 
reward  for  their  apparent  altruism. 

It  is  instructive  to  notice  M.  Pieron's  general  conclusion 
that,  as  ant-evolution  becomes  more  complex,  the  members 
of  the  community  become  more  and  more  dependent  on 
one  another.  The  species  which  are  most  thoroughly 
self-sufficient  are  the  most  successful  species,  as  far  as 
numbers  and  distribution  are  indicative  of  success.  On 
the  other  hand,  those  that  show  slave-keeping  and  parasitic 
habits  have  smaller  numbers  and  sparser  distribution. 
'  It  is  evident  that  when  ultra-civilization  degenerates 
into  slavery  and  parasitism  it  is  neither  good  for  man  nor 
ant '. 

The  records  of  studies  on  ants  make  quite  a  good-sized 
library,  but  we  have  looked  into  the  ant-hill  enough  for 
our  purpose  of  illustrating  some  of  the  features  of  an  animal 
society — division  of  labour,  subordination  of  the  individual 
to  the  whole,  a  capacity  for  unified  action  and  co-operation. 
As  we  have  had  to  say  so  often,  the  more  we  know  about 
it  the  more  the  wonder  grows.  The  social  life  seems  so 
intricate  that  we  wonder  how  it  could  have  evolved  at  all. 
Yet  let  us  look  at  it  in  one  of  the  simplest  expressions. 
There  is  a  Mediterranean  ant,  Aphanogaster  sardoa,  which 
illustrates  what  may  be  called  an  incipient  societary  form. 
According  to  Dr.  Krause-Heldrungen  these  ants  live  in 
holes  in  the  ground  and  do  not  build.  Nor  do  they  store 
or  entertain  guests.  Huddling  together  is  their  form  of 
sociality.  They  form  living  balls,  ant  interlocked  with 
ant  by  the  mandibles  and  tarsal  joints,  and  they  hold  the 
eggs,  larvae,  and  pupae  in  the  middle.  It  is  almost  like 
a  diagram  of  a  primitive  society  and  certainly  matri- 
archal !  A  ball  consists  of  three  hundred  to  a  thousand 


332  THE  WONDER  OF  LIFE 

individuals  ;  males  have  not  been  found  ;  and  the  investi- 
gator found  only  one  queen.  In  winter  the  ball  is  very 
stiff  and  is  slow  to  relax  when  it  is  unearthed.  The  whole 
communal  life  is  summed  up  in  huddling  together.  In 
summer,  however,  the  ball  is  naturally  more  plastic,  it  is 
always  being  unmade  and  remade. 

When  we  apply  a  term  like  '  social  instinct '  to  ants  and 
the  like,  we  are  probably  quite  accurate  if  we  mean  that 
they  have  a  hereditary  disposition  to  act  in  concert,  but 
there  is  a  danger  in  the  term  since  we  also  speak  of  our  own 
'  social  instincts  ',  meaning  something  much  more  complex 
than  the  ants.  But  in  avoiding  the  Scylla  of  anthro- 
pomorphism, it  is  unnecessary  to  fall  into  the  Charybdis  of 
mechanism.  For  ants  have  a  good  associative  memory,  they 
are  able  to  profit  by  experience,  they  act  co-operatively  and 
they  are  born  with  a  predisposition  towards  social  action. 

There  is  no  doubt  that  smell  counts  for  much  in  the 
ant  community.  Each  species  seems  to  have  its  charac- 
teristic odour,  just  as  the  Chinese  say  of  the  English,  who 
appear  to  them  to  smell  of  sheep.  It  is  by  the  scent  that 
the  intruding  ant  is  detected,  but  if  it  has  been  steeped 
in  an  essence  made  from  the  species  into  whose  nest  the 
experimenter  introduces  it,  then  it  is  welcomed.  This  does 
not  in  the  least  indicate  automatism  of  behaviour ;  it  is 
an  '  upsetting '  experiment  such  as  might  baffle  even  a 
clever  dog.  The  mistake  corresponds  to  that  made  in 
mankind  when  disguise  appealing  to  the  visual  sense  is 
almost  perfect. 

While  it  may  be  erroneous  to  speak  of  the  members  of 
the  ant-hills  being  '  animated  with  a  common  purpose ', 
and  while  there  is  a  good  deal  of  individualism  on  the  sly, 
it  appears  to  us  to  be  going  to  the  opposite  extreme  to  see 


THE  WEB   OF  LIFE  333 

in  the  co-operation,  e.g.  of  sewing  two  leaves  together 
or  of  carrying  a  heavy  burden,  nothing  more  than  the 
'  coincidence  of  purely  individual  activities  '.  Of  course 
the  activities  must  be  individual,  just  as  in  a  human 
society,  but  they  may  be  combined  in  a  joint  enterprise 
whose  result  is  for  the  benefit  of  the  community  rather 
than  of  the  single  life. 

Termites. — Parallel  to  the  true  ants  in  their  social  life, 
very  divergent  in  almost  every  other  respect,  are  the  so- 
called  '  white  ants  '  or  Termites  of  warm  countries — 
Africa,  India,  Australia,  etc.  They  are  usually  referred 
to  the  order  Neuroptera,  whereas  the  true  ants  are  Hymen- 
opterous.  While  there  is  great  variety  in  their  social 
organization,  it  may  be  said  that  the  Termite  community 
usually  consists  of  (1)  workers,  (2)  soldiers,  and  (3)  the 
reproductive  individuals,  or  kings  and  queens.  In  most 
cases  there  is  but  one  mature  royal  pair,  around  which 
the  life  of  the  community  centres ;  but  numerous  young 
'  kings  '  and  '  queens  '  are  produced,  which  are  winged 
and  leave  the  termitary  after  a  few  days  in  great  swarms 
which  often  come  to  nought.  The  mature  '  kings  '  and 
'  queens '  lose  their  wings.  The  organization  is  compli- 
cated in  various  ways,  for  instance  by  the  occurrence  of 
what  Grassi  called  complementary  kings  and  queens,  which 
the  workers  keep  in  reserve  lest  anything  befall  the  reigning 
pair.  They  are  kept  in  a  somehow  inhibited  state  of 
development,  but  can  be  brought  up  to  the  reproductive 
level  in  a  short  time. 

The  workers  illustrate  arrested  development ;  they 
may  be  regarded  as  '  permanent  children '  of  both 
sexes,  whereas  the  workers  among  ants  and  bees  are  all 
arrestments  on  the  female  side. 


334  THE  WONDER  OF  LIFE 

The  soldiers  are  quite  1  ke  the  workers  when  they  are 
hatched,  but,  while  they  also  suffer  arrestment,  they 
develop  on  a  line  of  their  own  with  very  large  heads  and 
jaws.  It  is  noteworthy  that  the  soldiers  of  different 
species  differ  much  more  than  the  workers  do,  and  that 
there  are  no  transitional  forms  between  soldiers  and 
workers.  It  must  also  be  noticed  that  the  title  '  soldiers  ' 
is  in  many  cases  at  least  a  courtesy  title,  for  the  workers 
usually  fight  much  better  and  the  militariness  of  the 
'  soldiers  '  is  often  exhausted  in  looking  on  ! 

The  erection  of  a  substantial  and  enduring  termitary 
must,  we  think,  have  had  great  significance  in  the  evolution 
of  the  complex  Termite  community.  For  it  is  a  permanent 
product  outside  the  organism,  part  of  the  social  heritage, 
enregistering  customs.  It  is  often  strong  enough  for  a 
man  to  stand  on,  and  it  shows  considerable  complexity 
of  architecture.  There  is  the  outside  wall,  with  passages 
in  it,  and  sometimes  tunnels  in  which  fungi  are  grown ; 
there  is  the  royal  chamber  where  the  king  and  queen  are 
imprisoned  ;  there  is  the  nursery — a  well- ventilated  apart- 
ment sometimes — where  the  young  are  reared ;  there  are 
store-chambers,  ventilating  shafts,  cellars  underground, 
and  sometimes  an  eerie  chamber  where  the  reserve  '  kings  ' 
and  '  queens '  are  kept.  One  of  the  most  interesting 
features  has  to  do  with  the  method  of  construction,  for 
in  many  species  the  scaffolding  of  chewed  wood  is  made  first, 
the  filling  in  comes  next,  and  there  is  a  final  smoothing 
and  pointing. 

The  industry  of  the  community  is  prodigious.  In  many 
cases  there  is  no  resting  by  day  or  night,  and  we  cannot 
find  any  parallel  except  in  some  highly  evolved  urban 
conditions  where  we  have  shops  and  restaurants  and  even 


THE   WEB   OF   LIFE  335 

factories  that  never  close,  but  go  on  night  and  day  without 
ceasing.  In  most  cases,  the  night  is  the  busiest  time, 
for  Termites  are  distinctly  nocturnal. 

Enumeration  is  always  interesting.  Messrs.  Andrews 
and  Middleton  counted  the  comings  in  and  goings  out  with 
great  patience. 

'  In  one  case  the  number  of  Termites  going  into  the  nest 
each  hour  varied  from  1,702  between  1  and  2  p.m.  to 
8,100  between  2  and  3  a.m.,  while  in  the  same  case  the 
numbers  going  out  of  the  nest  were  1,194  between  12  noon 
and  1  p.m.  and  6,820  between  1  and  2  a.m.' 

Thus  the  traffic  in  the  arcades  of  the  termitary  is  greatest 
in  the  middle  of  the  night,  and  least  at  noon. 

Very  striking  in  the  Termite  community  is  the  specializa- 
tion of  reproduction.  It  is  practically  left  to  the  royal 
pair.  In  some  cases  there  are  several  royal  pairs.  They 
alone  are  reproductive  ;  all  the  thousands  of  other  members 
are  productive  and  protective  and  domestic.  The  queen 
is  like  a  grotesque  caricature  of  fertility.  As  Smeathman 
observed,  the  abdomen  becomes  dilated  with  eggs  until 
it  is  '  fifteen  hundred  or  two  thousand  times  the  bulk  of 
the  rest  of  her  body,  and  twenty  or  thirty  thousand  times 
the  bulk  of  a  labourer '.  '  It  is  always  protruding  eggs 
to  the  amount  (as  I  have  frequently  counted  in  old  queens) 
of  sixty  in  a  minute,  or  eighty  thousand  and  upward  in 
one  day  of  twenty-four  hours '.  Yet  associated  with 
this  fertility  is  an  equally  surprising  longevity,  for  the  queen 
may  live  for  several  years.  The  male's  tenure  of  life  is 
unknown. 

Another  fact  worth  thinking  about  is  the  convergence 
in  some  details  between  the  ant  community  and  the  white 


336  THE  WONDER  OF   LIFE 

ant  community.  In  both  we  find  the  curious  entertaining 
of  other  insects  as  guests  and  pets ;  in  both  we  find  the 
growing  of  fungi  for  food.  Some  Termites  make  a  sponge- 
like  maze  of  chewed  wood  and  a  mould  is  grown  on  the 
walls  of  the  tunnels  which  is  greatly  enjoyed  by  the  culti- 
vators. It  probably  supplements  their  other  food,  supply- 
ing some  constituent  otherwise  lacking  or  scarce. 

Signalling  among  White  Ants. — It  has  been  known 
for  a  long  time  that  the  soldiers  of  some  kinds  of 
Termites  are  able  to  give  an  alarm-signal  when  they  are 
frightened  or  distracted.  Thus,  as  far  back  as  1779  Konig 
described  Hodotermes  convulsionarius  striking  dry  leaves 
with  its  mandibles.  Smeathman,  Haviland  and  Sjostedt 
have  also  reported  the  occurrence  of  indubitable  signalling. 
Smeathman  watched  the  building  of  the  wall  of  a  termitary, 
and  noticed  that  soldiers  standing  on  guard  struck  the 
building  with  their  mandibles  at  intervals  of  one  or  two 
minutes  and  made  a  sort  of  crackling  noise.  This  sign 
seemed  to  encourage  the  workers  to  increased  industry, 
and  to  reassure  them  in  some  sort  of  way.  When  an 
attack  was  made  on  the  ant-hill  the  workers  disappeared 
into  the  internal  passages  and  the  soldiers  made  a  sortie. 
After  things  were  settled  up  again,  the  workers  returned 
to  their  labours,  and  the  sentinels  to  their  signalling. 
Prof.  Escherich  relates  that  when  he  was  having  a  Ceylon 
termitary  of  Termes  bellicosus  opened  with  a  pickaxe, 
he  heard  a  protesting  noise  from  within — like  that  made 
by  a  rattlesnake.  The  noise  was  also  heard  by  the  native 
who  wielded  the  instrument.  He  heard  it  and  fled,  leaving 
Escherich  to  continue  the  operations. 

When  Prof.   Bugnion  and  three  others  were  recently 
exploring  in  Ceylon,  moving  cautiously  amongst  dense 


THE  WEB   OF  LIFE  337 

vegetation,  they  began  to  hear  a  curious  rustling  noise 
which  at  first  suggested  the  presence  of  a  cobra.  Advanc- 
ing carefully  they  found  no  hint  of  any  snake,  but  traced 
the  sound  to  a  colony  of  Termes  obscuriceps  which  had 
formed  its  galleries  on  the  large  fallen  leaves  of  a  Bread 
Tree  (Artocarpus).  The  sound  was  caused  by  the  Termites 
striking  the  under-surface  of  the  dry  leaves.  On  another 
occasion  about  a  hundred  Termites  took  possession  of 
a  little  desk  in  Bugnion's  office,  and  they  used  to  answer 
back  to  knocks  from  without. 

What  is  it  that  happens  ?  Prof.  H.  von  Buttel-Keepen 
helped  Bugnion  in  the  inquiry,  and  showed  what  one  has 
to  do  to  make  the  white  ants  signal — '  pour  faire  parler 
les  Termites '.  Part  of  a  termitary  is  placed  on  a  platter 
and  covered  with  a  sheet  of  strong,  firm  paper.  The 
soldier  Termites  collect  on  the  under-side  of  the  paper 
and  answer  back  to  every  signal.  Whenever  the  paper 
vibrates  they  strike  it  repeatedly  with  their  mandibles 
or  with  their  chin  (the  basal  piece  of  the  third  pair  of 
mouth-appendages,  which  is  exaggerated  and  hard  in 
the  soldiers).  What  happens  in  nature  is  that  dry  leaves 
or  the  like,  struck  by  repeated  blows,  repercussate  like 
resonating  plates.  The  thin  wooden  partitions  in  the 
interior  of  the  termitary  will  also  have  the  same  capacity 
of  transmitting  vibrations.  It  seems  that  the  sound  pro- 
duced differs  considerably  in  different  species.  To  different 
audiences  it  suggested  the  hiss  of  a  snake,  a  crackling,  a 
rattling,  and  the  far-off  chirping  of  a  cricket.  It  is  charac- 
teristic of  soldiers  of  the  genus  Termes  and  is  always  due 
to  minute  blows  on  a  resonating  surface.  It  is  well  illus- 
trated by  the  Indian  Termes  esiherce  (the  same  as  Konig's 
Hodotermes  convulsionarius),  which  makes  long  horizontal 

z 


338  THE  WONDER  OF  LIFE 

galleries,  with  fungus-growing  labyrinths,  but  no  hills. 
The  soldiers  are  very  large  and  aggressive,  and  when  dis- 
turbed make  a  prolonged  noise  like  the  crackling  of  withered 
leaves  when  one  treads  on  them.  It  is  produced  by 
raining  tiny  blows  on  the  dry  surface  of  the  fungus-laby- 
rinths. 

This  type  of  signal  is  to  be  distinguished  from  another 
kind,  a  soundless  signal,  by  which  the  soldiers  seem  to 
give  orders  to  passing  workers.  The  insect,  firmly  poised 
on  its  legs,  with  the  head  raised  and  the  body  slightly 
oblique,  shakes  itself  for  an  instant  convulsively.  It 
signals  with  a  shiver.  This  is  probably  very  common 
among  Termites,  and  is  particularly  well  illustrated  in 
Eutermes,  a  genus  in  which  the  structure  of  the  soldier's 
head  is  not  suited  for  drumming.  It  need  hardly  be  said 
that  the  signalling  noise,  which  is  of  much  psychological 
interest,  is  not  to  be  confused  with  a  more  commonplace 
sound — of  minute  grating — which  is  often  heard  in  the 
silence  of  the  night.  That  is  the  sound  made  by  the 
Termites  as  they  chew. 

If  the  signals  of  the  soldier-Termites  are  to  be  effective, 
they  must  be  heard  or  felt,  and  this  is  borne  out  by 
observations  in  the  field,  by  the  answers  that  the  tenants 
of  Bugnion's  desk  made  to  taps  from  without,  and  by  the 
anatomical  demonstration  of  a  well  innervated  organ 
which  is  probably  peculiarly  sensitive  to  vibrations.  That 
the  signalling  is  signalling  seems  indubitable,  and  it  must 
be  regarded  as  analogous  not  so  much  to  the  love-signals 
of  the  death-watch,  who  taps  on  the  wainscot,  as  to  the 
thumps  on  the  ground  by  which  rabbits  indicate  the 
approach  of  danger. 


THE  WEB  OF  LIFE  339 

THE  BEE-HIVE 

We  are  probably  nearer  the  truth  in  thinking  of  the 
bee-hive  as  a  large  family  rather  than  as  a  society,  but 
this  makes  little  difference,  for  whatever  the  nature  of 
the  communal  life  may  be  it  is  certainly  far  away  from 
anything  human.  It  is  run  on  predominantly  instinctive 
lines,  whereas  a  human  society  is  predominantly  intelli- 
gent. Comparisons  between  the  bee-hive  and  the  city 
are  apt  to  be  fallacious  analogies. 

So  much  has  been  written  in  regard  to  the  life  of  the 
bee- hive  that  we  shall  not  do  more  than  call  attention  to 
a  few  essential  features.  It  may  be  more  useful  to  con- 
sider the  question  of  evolution. 

As  every  one  knows,  the  hive  shows  polymorphism. 
There  are  the  fertile  females  or  queens  ;  the  males  or 
drones  ;  and  the  sterile  females  or  workers — a  sort  of 
third  sex.  These  three  types  differ  in  many  details,  and 
it  is  noteworthy  that  since,  the  drones  develop  from  un- 
fertilized ova — having  a  mother  but  no  father — their 
inheritance  of  male  reproductive  organs  and  masculine 
secondary  characters  must  be  handed  on  through  the 
queens.  Besides  the  structural  polymorphism  there  is 
considerable  division  of  labour.  The  queens  and  drones 
are  wholly  reproductive ;  the  workers  may  be  foragers, 
who  go  afield  collecting,  or  nurses  who  attend  to  the  queen 
and  the  young.  The  workers  have  finely  developed  brains, 
better  than  those  of  the  queen,  probably  because  more 
exercised,  and  they  are  distinctively  females,  being  occa- 
sionally fertile.  Both  queens  and  workers  develop  from 
fertilized  ova,  the  difference  in  result  apparently  depend- 
ing on  the  quantity  and  quality  of  food  given  to  the  grubs. 
In  short,  every  worker  is  a  potential  queen,  arrested  at  a 


340  THE  WONDER  OF  LIFE 

certain  point  as  regards  her  reproductive  system.  A 
notable  fact  is  the  short  Life  of  the  individual  workers, 
who  only  last  two  or  three  months  in  the  arduous  summer  ; 
their  brain-cells  show  signs  of  chronic  fatigue  and  pass 
eventually  beyond  the  limits  of  recuperation.  This  is  the 
seamy  side  of  the  bee's  much-praised  industry.  With 
all  its  getting,  it  gets  not  wisdom,  but  foolishness. 

Three  events  are  alike  remarkable — the  nuptial  flight, 
the  swarming,  and  the  death  of  the  drones.  In  the  nuptial 
flight,  a  young  queen,  arrived  at  her  maturity,  passes  from 
the  hive  followed  by  a  number  of  drones.  One  of  these 
is  successful  in  overtaking  her  and  in  fertilizing  her.  In 
many  cases  he  will  be  the  most  vigorous  and  effective, 
which  will  be  the  better  for  the  race,  for  while  he  and  all 
the  others  perish,  he  is  the  father  of  another  generation, 
while  they  have  lived  and  died  without  having  done  any- 
thing but  feed  and  fly.  The  store  of  sperms  received  by 
the  f ertilized  queen-bee  may  last  for  a  year  or  two,  and  it 
depends  on  the  way  in  which  she  lays  her  eggs  whether 
they  are  fertilized  or  not. 

The  swarming  illustrates  an  interesting  solution  of  the 
population  question.  When  the  numbers  in  the  hive  have 
greatly  increased,  the  old  queen  goes  off  with  the  super- 
abundance of  the  population,  and  founds  a  new  community. 
It  occasionally  happens  that  this  settles  down  in  an  im- 
possible place  and  comes  to  naught,  but  Bonnier  describes 
a  successful  nesting  in  a  tree — a  very  interesting  case,  since 
the  making  of  the  combs  had  to  be  greatly  modified  to  suit 
the  new  conditions. 

The  mortality  of  the  drones  is  partly  due  to  the  shortage 
of  supplies  towards  the  end  of  summer,  for  they  depend  on 
what  the  workers  give  them,  and  the  stores  are,  of  course, 


THE  WEB   OF  LIFE  341 

inviolate.  The  number  of  drones  is  also  reduced,  as 
we  have  just  noted,  by  the  nuptial  flight.  But  there 
remains  for  the  survivors — whether  adults  or  larvae — a 
tragic  death  at  the  hands  of  the  workers  and  nurses.  As 
the  result  of  this  Lycurgan  tragedy  there  are  no  drones  left 
at  the  end  of  the  season.  It  seems  rather  noteworthy  that 
while  the  venom  of  a  cobra  is  not  deadly  to  another  cobra, 
the  formic  acid  of  the  bee's  sting  seems  to  be  fatal  to 
another  bee. 

EVOLUTION  OF  SOCIAL  BEES 

Let  us  inquire  into  the  evolution  of  social  bees,  utilizing 
especially  the  studies  of  Dittrich  and  Buttel-Reepen. 
The  social  mode  of  Hie  is  marked,  as  every  one  knows,  by 
three  distinctive  features :  (1)  the  differentiation  of 
fertile  females  (queens)  and  normally  non-fertile  females 
(workers) ;  (2)  the  utilization  of  wax  for  some  kind  of 
comb  ;  and  (3)  the  accumulation  of  stores,  especially  of 
pollen  and  nectar.  Between  the  highly  evolved  social 
life  of  the  hive-bees  and  the  life  of  the  solitary  bees  there 
are  many  transitional  stages,  and  although  we  cannot 
display  the  pedigree  of  the  hive-bee,  nor  arrange  the  stages 
in  what  was  the  actual  historical  sequence,  we  can  see  how 
very  gradual  the  transition  from  solitary  to  social  may  have 
been.  The  following  is  Dittrich's  series  : — 

I. — Bees  living  alone  : — 

(a)  The  mother  dies  after  egg-laying  and  providing  food 
for  the  larvae,  but  without  ever  seeing  the  brood. 

1.  The  nests  are  formed  quite  apart :  Prosopis,  Ceratina, 

Osmia  papaveris,  etc. 

2.  The  females  work  independently,  but  the  nests  are 

formed  in  colonies,  and  there  may  be  mutual  aid 


342  THE  WONDER  OF  LIFE 

against  attack :  Andrena,  Anthophora,  Chalico- 
doma,  Osmia,  etc. 

3.  Females,  or  females  and  males,  hibernate  in  com- 

panies :  Halictus  morio,  Xylocopa. 

4.  Two  or  more  females  use  a  common  hole  of  refuge  : 

Panurgus,  Halictus,  etc. 

(6)  The  mother  survives  to  see  the  brood  and  watches 
over  the  nest. 

5.  Halictus  sexcinctus. 

6.  The  cells  form  a  comb,  Halictus  quadricinctus. 

7.  The  first-born  young  are  all  females,  they  work  in 

the  old  nest,  and  parthenogenetically  produce 
males  and  females  :  Halictus  scabiosus. 

8.  The  next  stage,  according  to  Buttel-Reepen,  should 

be  that  in  which  the  mother  and  the  parthenogene- 
tically reproductive  young   work  together  in  the 
old  nest,  but  a  representative  of  this  stage  has  not 
yet  been  found. 
II. — Bees  living  socially  : — 

9.  The  fertilized  female    hibernates  alone ;    forms  in 

Spring  a  new  nest ;  is  helped  by  a  brood  of  workers 
which  are  parthenogenetically  reproductive  only 
in  isolated  cases ;  and  produces  in  the  course  of 
summer  males  and  more  females.  In  autumn  the 
whole  society  dies  off  except  the  fertilized  females  : 
Humble-bees. 

10.  Permanent  societies,   with  imperfect  combs  :    the 

tropical  species  of  Melipona  and  Trigona. 

11.  Permanent   societies,    with   perfect   combs :     Apis 

mellifica,  A.  dorsata,  A.  florea. 

This  very  interesting  series  does  not  of  course  disclose 
the  impulses  which  led  from  one  mode  of  life  to  another, 


THE  WEB  OF  LIFE  343 

but  it  does  show  how  gradually  the  state  of  affairs  in  the 
hive-bee  community  might  evolve.  This  becomes  even 
more  convincing  when  we  go  into  detail;  thus,  among 
humble-bees,  some  (in  the  North)  are  quite  solitary — female 
and  males,  without  any  workers  ;  some  (e.g.  in  Britain 
and  Germany)  form  temporary  summer  societies  ;  some 
(e.g.  in  Corsica  and  the  Balearic  Islands)  partially  sur- 
vive the  winter  as  societies  ;  and,  finally,  some  tropical 
forms  (according  to  R.  von  Jhering)  are  permanently 
social. 


FIG.  55. — Section  of  nest  of  Humble-Bee,  Bombus  lapidarius.  (After 
Wagner.)  To  the  outside  there  is  a  felt  work  of  grass  stems  and  the 
like.  The  entrance  is  to  the  right  on  the  level  of  the  ground.  In 
the  middle  of  the  cavity  of  the  nest  of  this  species,  lies  a  dome  of 
wax,  above  but^not  below  the  cells  which  contain  the  pupae. 
The  entrance  is  shown  by  which  the  queen — still  the  only  tenant 
— enters  to  brood  over  the  cells  or  to  give  honey  to  the  larvae. 
In  a  finely  made  nest  the  roof  of  the  cavity  of  the  neat  is  plastered 
with  wax,  where  the  figure  shows  a  dark  line. 

We  have  figured  a  stage  in  the  history  of  the  nest  of  the 
humble-bee  (Bombus).  In  the  early  Spring  the  queens, 
who  are  the  only  survivors  of  the  previous  summer's  colony, 
awaken  from  their  winter  sleep,  and  make  for  the  early 
flowers,  such  as  the  catkins  of  the  dwarf  willow.  Each 
seeks  out  a  nesting-place  underground,  perhaps  in  the 


344  THE  WONDER  OF  LIFE 

deserted  burrow  of  a  field-mouse.  In  the  middle  of  a 
ball  of  grass,  leaves  and  the  like,  some  nectar  and  pollen 
are  collected,  and  on  this  floor  a  cell  or  cradle  of  brown 
wax  is  built.  Some  eggs  are  laid  in  it  and  a  lid  is  put  on. 
The  queen  broods  over  this  cradle,  till  in  four  days  or  so  the 
grubs  emerge.  These  soon  use  up  the  food  in  the  cradle 
and  more  has  to  be  put  in  through  a  hole  in  the  lid.  More- 
over, the  cradle  has  to  be  enlarged,  till  it  is  as  big  as  a 
walnut.  In  about  a  week  after  hatching,  the  grubs  pass 
into  a  quiescent  pupa-state  within  papery  cocoons,  upright 
within  the  cradle.  The  mother  bites  the  waxen  walls 
away  and  broods  again  over  the  cocoons.  In  about  twelve 
days  worker-bees  emerge,  who  assist  the  queen,  building 
new  cradles,  collecting  food,  and  nursing  a  new  generation. 
Besides  the  workers  there  are  drones  or  males,  who  leave 
the  nest  as  soon  as  they  can  fly  and  fend  for  themselves 
outside.  Then  there  are  young  queens,  who  fly  off  by  and 
by  on  what  is  called  their  nuptial  flight,  in  which  they 
are  joined  by  the  drones.  They  are  the  mothers  of 
another  year. 

As  a  single  instance  of  more  elaborate  construction  we 
have  inserted  a  figure,  from  Janet,  of  the  paper  nest 
of  a  wasp  (Vespa  media).  The  nest  in  this  case  was 
hung  to  a  leaf,  but  to  begin  with  to  a  twig  seen  in  the 
centre.  The  door  is  to  the  left  side  below.  The  walls  are 
made  of  numerous  (eighteen)  overlapping  envelopes  of 
the  chewed  wood  which  forms  the  wasp-paper.  About 
ten  of  these  have  been  torn  away  below  to  make  room  for 
the  combs.  The  first  comb  (2)  was  about  four  inches  in 
diameter,  and  showed  five  concentric  areas  of  cells,  some 
the  cradle  of  one  young  wasp,  others  used  twice,  mostly 
for  workers,  but  partly  for  males.  An  axial  support  (3)  leads 


THE  WEB^OF  LIFE  345 


Fia.  56. — Nest  of  a  Wasp,  Vespa  media,  in  vertical  section.  1 .  One  of  the 
outer  envelopes.  2.  A  cell  of  the  first  comb.  3.  The  axial  sup- 
port. 4.  A  cell  of  the  second  comb.  5.  A  cell  of  the  third  comb. 
(After  Janet.) 


to  the  second  comb  (4),  which  shows  cells  of  various  sizes. 
Another  support  leads  to  the  third  comb  (5),  which  bore 
thirty-three  cells  for  queens  and  seven  for  males,  but  was 
not  completed  peripherally.  The  original  queen  had  dis- 
appeared ;  the  nest  included  about  thirty  young  queens, 
forty  males,  and  sixty  workers. 

Criteria  of  an  Animal  Society. — As  we  review  the 


346  THE  WONDER  OF  LIFE 

series  of  social  animals  we  find  every  grade  between  mere 
gregariousness  and  well-defined  societary  forms,  and  no 
one  can  pretend  that  any  hard  and  fast  line  can  be  drawn. 
There  are,  however,  certain  features  whose  presence,  in 
whole  or  in  part,  is  diagnostic  of  a  real  society.  (1)  The 
first  of  these  is  the  capacity  for  corporate  action.  When 
a  herd  of  herbivores  unites  against  the  attack  of  carnivores 
when  the  little  cliff-swallows  unite  in  a  mob  and  drive  off 
the  falcon,  when  a  band  of  monkeys  nearly  tear  to  pieces 
the  eagle  which  has  swooped  upon  one  of  their  number, 
when  the  wolves  hunt  in  packs,  and  the  pelicans  form  a 
living  seine-net,  wading  inwards  in  a  diminishing  crescent 
towards  the  shore,  there  is  struck  beyond  doubt  the  note 
of  society. 

Bees  will  act  together  to  deal  with  an  intruder  who  has 
got  into  the  hive,  perhaps  sealing  him  up  with  wax ;  they 
will  combine  to  carry  away  some  foreign  object ;  they  appear 
to  practise  division  of  labour ;  they  somehow  make  one 
another  aware  of  valuable  discoveries  of  nectar. 

Yet  one  must  not  be  too  generous.  Thus,  to  take  a 
single  example,  there  may  be  some  truth  in  the  view  of 
Netter  that  the  ventilating  bees  who  make  a  current  by 
their  wings  at  the  entrance  to  the  hive  are  bees  in  respiratory 
difficulties. 

Spiders  are  characteristically  individualistic  except  in 
their  maternal  care,  but  a  few  social  species  are  known, 
e.g.  Stegodyphus  gregalis  from  South  Africa,  S.  sarasinorum 
from  Madras,  and  Uloborus  republicanus  from  Venezuela. 
The  Madras  form  is  described  by  N.  S.  Jambunathan  as 
forming  a  sponge-like  nest  of  ramified  canals,  which  is  often 
attached  to  the  branches  of  trees  or  to  the  leaves  of  the 
prickly  pear.  The  number  in  a  nest  varies  from  40  to  100, 


THE  WEB  OF  LIFE  347 

males  and  females  usually  in  the  proportion  of  7  :  1,  though 
sometimes  there  are  still  fewer  females.  It  is  said  that 
these  spiders  sometimes  work  together,  e.g.  in  securing  a 
victim,  and  that  they  share  the  food  without  quarrel. 
There  is  no  marked  dimorphism  of  the  sexes,  which  live 
together  amicably — in  a  sort  of  millennium  among  spiders. 
The  maternal  care  is  very  highly  developed. 

(2)  Another  diagnostic  feature  is  the  existence  of  division 
of  labour,  implying  some  measure  of  mutual  dependence. 
The  different  types  in  the  ant-hill,  the  termitary,  and  the 
bee-hive  are  the  best  illustrations,  but  we  see  the  same 
'  idea '  in  the  posting  of  sentinels,  which  is  well  known 
among  both  birds  and  mammals — witness,  for  example, 
rooks  and  monkeys. 

(3)  In  some  cases  we  seem  to  be  warranted  in  speaking 
of  social  conventions.     Thus  in  certain  species  of  ants  it 
appears  to  be  the  unwritten  law  that  the  full  must  not  refuse 
to  feed  the  hungry,  and  in  a  rookery  it  seems  to  be  an  estab- 
lished convention  that  after  a  nest  has  reached  a  certain 
stage  in  its  construction  it  is  no  longer  legitimate  to  steal 
sticks  from  it. 

In  connexion  with  the  origin  of  animal  societies  there  is 
probably  a  hint  to  be  got  from  the  occurrence  of  temporary 
socializations.  We  get  an  illustration  of  this  when  migrat- 
ing birds  form  a  company — sometimes  relatively  small,  as 
when  the  V-shaped  band  of  wild  geese  passes  '  honk-honk- 
ing '  overhead;  sometimes  innumerable,  as  when  vast 
flocks  of  plover  pass  southwards  in  the  autumn.  Another 
illustration  may  be  found  in  the  march  of  the  lemmings 
when  they  are  compelled  by  over-population  and  the  conse- 
quent dearth  of  food  to  leave  their  homes  ;  and  it  is  inter- 
esting to  notice  what  audacity  and  persistence  the  force  of 


348  THE  WONDER  OF  LIFE 

numbers  seems  to  lend  the  little  rodents  on  these  occasions. 

The  advantages  that  animals  gain  by  forming  societies 
are  many.  They  gain  a  firmer  footing  in  the  struggle 
for  existence.  There  is  strength  in  numbers,  as  is  well 
illustrated  by  the  ants — a  little  people,  but  greatly  dreaded. 
There  is  strength  in  co-operation,  for  several  can  effect 
what  a  single  individual  need  not  even  attempt.  Several 
ants  together  will  carry  a  large  spider.  When  there  is 
division  of  labour  and  some  exchange  of  services,  the  advan- 
tage grows.  Thus  it  is  obviously  great  gain  to  have  senti- 
nels posted,  to  have  some  members  at  home  while  others 
are  abroad,  to  have  a  leader  and  a  change  of  leader  in  the 
migrating  phalanx.  Sometimes  the  economy  of  the  divi- 
sion of  labour  is  startling.  Thus  Fabre  has  told  us  of  the 
mother  Halictus  bee,  who,  when  she  is  too  exhausted  for 
maternity,  becomes  the  concierge  of  the  establishment, 
admitting  and  excluding  visitors  as  her  discretion  directs. 

There  appears  to  be  an  intellectual  advantage  in  socia- 
lity, if  we  may  argue  from  the  fact  that  many  social  ani- 
mals show  a  high  development  of  wits.  The  three  clever- 
est kinds  of  birds  are  rooks,  cranes,  and  parrots,  and  they 
are  notably  social.  There  is,  of  course,  a  danger  of  putting 
the  cart  before  the  horse,  for  it  may  be  that  the  sociality 
is  in  part  the  expression  of  good  brains.  It  may  also  be 
argued  that  the  non-gregarious  crow  is  just  as  clever  as  the 
social  rook,  and  many  analogous  instances  might  be  given. 
On  the  other  hand,  beavers  belong  to  the  slow-witted  order 
of  Rodents,  and  though  the  reports  of  their  sagacity  have 
been  greatly  exaggerated,  there  is  no  doubt  that  they  show 
considerable  intellectual  ability.  The  probability  is  that 
both  points  of  view  are  right ;  the  formation  of  a  society 
implies  a  certain  fineness  of  intellectual  or  instinctive 


THE   WEB   OF  LIFE  349 

fibre,  but  the  social  life  improves  upon  this  up  to  a  certain 
point.  Every  one  knows  how  much  the  mind  of  adult 
man  is  a  social  product. 

Another  advantage  that  must  mean  much  is  bound  to 
accrue  when  there  is  any  sort  of  permanent  product  which 
is  handed  on  from  generation  to  generation  as  a  sort  of 
external  heritage.  The  loosely  built  ant-hill,  the  hard 
edifice  of  the  termitary,  the  honeycomb  of  the  bee,  express 
a  sort  of  communal  art  and  a  registration  of  achievement, 
and  must  be  of  importance  in  the  continuance  of  the  social 
life.  In  the  more  intelligent  types  there  is  probably  some- 
thing in  the  way  of  social  tradition  which  secures  a  persist- 
ent strategy,  as  when  beavers  cut  a  long  canal  through  an 
island  or  gradually  build  up  a  very  strong  dam. 

The  defensive  value  of  social  organization  is  very  well 
illustrated  in  the  case  of  many  of  the  ants.  In  reference 
to  the  South  European  harvesting  ants  (Atta  structor  and 
Atta  Barbara)  Mr.  Moggridge  noticed  that  their  enemies 
treated  them  with  great  circumspection.  Lizards  eat 
only  the  winged  males  and  females  and  try  to  keep  out  of 
the  way  of  the  workers,  who  in  their  turn  do  their  best  to 
be  an  effective  bodyguard  to  the  winged  forms.  There  is 
a  large  proportion  of  soldiers,  some  of  which  are  literally 
walking  jaws,  always  ready  to  snap  and  to  hold  on  to  the 
death.  Of  another  enemy,  the  Tiger-beetles  (Cicindela), 
it  is  said  that  although  they  devour  the  workers,  they  keep 
out  of  the  way  of  the  main  body  and  look  after  the  stragglers 
only.  If  they  fail  to  catch  the  ant  at  the  strategic  point, 
just  behind  the  neck,  they  are  said  to  let  go  at  once,  as  if 
they  were  aware  that  if  the  ant's  jaws  once  close  on  any 
part  of  their  limbs  or  feelers  they  will  not  leave  go  again, 
even  after  death. 


350  THE  WONDER  OF  LIFE 

OTHER  ILLUSTRATIONS 

In  a  rookery  we  have  familiar  to  all  an  illustration  of 
communal  life  which  is  far  nearer  human  society  than  are 
the  more  elaborate  instinctive  integrates  of  ant  or  bee. 
Rooks  are  permanently  gregarious,  feeding  together,  fly- 
ing together,  and  nesting  together.  There  seems  no  doubt 
whatever  that  they  post  sentinels — a  devolution  of  duty 
which  is  in  itself  social.  And  there  appear  to  be  certain 
conventions  which  must  be  observed,  disregard  of  which  is 
punished. 

Hudson  gives  a  delightful  picture  of  the  simple  social 
life  of  the  Viscachas,  burrowing  Rodents  of  the  Pampas. 
Twenty  or  thirty  burrows  are  made  close  together,  as  in  a 
rabbit  warren.  The  earth  is  carried  off  for  a  short  distance 
and  may  form  a  mound  on  which  the  Viscachas  sit  in  the 
evening.  After  sunset  they  go  a- visiting  to  the  adjoining 
settlements,  and  their  well-trodden  paths  show  that  there 
is  much  coming  and  going.  They  seem  to  be  stupid  little 
creatures,  but  it  is  hard  to  deny  them  a  love  of  company. 
Hudson  says  he  doubts  if  there  is  any  four-footed  creature 
so  loquacious  as  this  little  Rodent,  or  with  a  dialect  so 
extensive.  Sometimes  the  farmer  fills  up  the  burrows  and 
tries  to  smother  the  Viscacha  villagers,  but  Hudson  relates 
that  when  the  visitors  come  at  night  they  try  vigorously 
to  dig  their  entombed  neighbours  out  again.  Surely  more 
than  a  touch  of  sociality. 

Much  that  is  exaggerated  has  been  said  in  regard  to 
beaver-villages,  but  there  is  no  doubt  that  individuals  co- 
operate in  relatively  gigantic  enterprises.  It  is  probable 
that  in  previous  ages  this  extremely  shy  animal  lived  in 
larger  communities  and  engaged  in  even  greater  endeavours. 
To  make  a  dam  half  a  mile  in  length,  or  to  cut  a  canal 


THE  WEB   OF  LIFE  351 

through  an  island  in  the  middle  of  a  river,  are  large  collec- 
tive tasks,  which  are  especially  interesting  because  they  do 
not  justify  themselves  greatly,  if  at  all,  until  they  are 


DOMESTICATION 

It  is  very  well  known  that  a  few  species  of  ants  treat 
certain  Aphides  or  green-flies  as  if  they  were  domestic 
animals.  They  '  milk '  them,  stroking  them  with  their 
antennae,  and  inducing  the  exudation  of  some  drops  of 
'  honey-dew. '  They  stable  them  underground  in  the  winter 
and  put  them  out  to  pasturage  again  in  the  early  summer. 
But  this  well-known  case  does  not  stand  by  itself. 

Many  years  ago  Fritz  and  Hermann  Miiller  described 
how  the  larvae  of  a  Membracid  (Potnia  or  Umbonia)  were 
used  as  milk-cattle  by  a  Brazilian  stingless  bee  (Trigona 
cagafogo).  The  bee  in  question  is  somewhat  remarkable 
for  its  tastes  ;  it  is  very  fond  of  oily  matters  and  frequents 
flowers  with  many  glands  ;  it  also  feeds  on  carrion  and  is 
attracted  to  rotten  cheese.  Its  popular  name  of  '  spit-fire  ' 
alludes  to  its  intensely  irritant  venom,  for  although  it  is 
stingless,  it  has  well-developed  poison-glands. 

Approximating  to  domestication  is  the  extraordinary 
relationship,  described  by  Viehmeyer,  between  a  species  of 
ant  from  Manila  (Camponotus  quadriseclus)  and  a  Lepidop- 
terous  pupa.  The  ant  makes  a  well-known  hanging  earthen 
nest  and  the  pupae  are  found  in  special  cells  in  the  centre. 
When  the  nest  was  broken  the  furious  ants  grouped  them- 
selves around  the  pupae  as  if  to  protect  them,  but  closer 
investigation  showed  that  their  anxiety  was  not  disinter- 
ested. At  the  posterior  end  of  the  pupa  there  is  a  curious 
chitinous  crater,  and  opening  into  this  a  gland  which  seems 


352  THE  WONDER  OF  LIFE 

to  secrete  a  sort  of  honey  dew.  It  looks  as  if  the  pupa 
served  as  a  food  purveyor  to  the  ants,  but  it  would  be  satis- 
factory to  have  some  observational  verification  of  this.  It 
would  also  be  interesting  to  know  whether  the  pupa  gets 
any  quid  pro  quo,  whether  the  winged  insect  when  it  emerges 
is  not  possibly  in  need  of  some  assistance  from  the  ants. 

F.  Le  Cerf  describes  a  remarkable  association  between 
a  Lycaenid  caterpillar  and  a  colony  of  ants  of  the  genus 
Cremastogaster.  The  case  was  discovered  by  MM. 
Alluaud  and  Jeannel  on  the  Kikuyu  escarpment.  Certain 
acacias  bear  numerous  nut-like  galls,  perforated  by  an 
orifice  about  1  mm.  in  diameter  through  which  the  ants 
go  out  and  in.  The  caterpillar  is  about  10  mm.  in  length, 
curiously  like  a  wood-louse  or  a  Chiton,  and  bearing  very 
peculiar  modified  hairs.  Its  mouth-parts  suggest  a 
vegetarian  diet,  and  it  probably  feeds  on  the  acacia  leaves 
which  the  ants  store.  It  could  not  possibly  get  out  of  the 
gall,  and  it  must  have  been  reared  there  by  the  ants. 

GUESTS  AND  PETS 

A  great  number  of  cases  are  now  known  where  small 
beetles  or  other  insects  live  in  terms  of  friendly  association 
with  ants.  One  of  the  most  extraordinary  cases  is  that  of 
the  cricket  genus  Myrmecophila,  some  species  of  which  have 
become  guests  of  ants.  Particular  guests  are  wont  to  be 
associated  with  particular  hosts  ;  thus  Myrmecophila  acer- 
vorum  is  usually  found  in  the  nests  of  the  black  ant,  Lasius 
niger,  and,  in  suitable  localities,  of  the  red  ant,  Myrmica 
rubra.  The  reason  for  the  picking  and  choosing  of  a  host 
is  probably  to  be  found  in  some  adaptation  in  the  relative 
size  of  host  and  guest.  The  little  crickets  get  shelter 
and  food  ;  they  lick  their  hosts,  who  give  up  some 


THE  WEB   OF  LIFE  353 

of  their  food ;  they  plunder  the  worker-ants  returning  to 
the  nest  with  spoils  ;  they  steal  from  the  newly-fed  larvae  ; 
they  insist  on  having  a  share  when  the  ants  are  eating ; 
and,  finally,  they  sometimes  demand  food  from  the  ants, 
raising  their  forelegs  in  a  peculiar  fashion.  In  this  move- 
ment and  in  that  of  the  antennae,  there  seems  to  be  some- 
thing like  an  imitation  of  the  ants'  movements,  but  in  other 
ways  their  movements  are  conspicuously  different.  Why 
the  ants  tolerate  them,  who  can  tell  ?  It  is  interesting  to 
note  that  M.  acervorum  is  purely  parthenogenetic,  and  it  is 
probable  that  some  other  species  are  partially  so.  The 
eggs  of  M.  acervorum,  and  probably  of  other  species,  are 
laid  in  the  nests  of  the  host,  and  the  fact  that  they  are  few 
in  number  and  large  in  size  with  much  yolk  may  perhaps 
be  correlated  with  the  safe  and  luxurious  conditions  which 
the  mothers  have  found  as  semi-parasites  in  the  ants'  nest. 
In  some  cases  of  '  myrmecophily  '  the  hosts  get  a  little  in 
the  way  of  quid  pro  quo,  but  what  return  do  these  little 
crickets  make  save  an  occasional  kiss  ?  It  is  easy  to  under- 
stand the  crickets  being  content,  but  why  the  ants  tolerate 
their  presence  is  a  mystery.  If  they  thought  of  it,  they 
could  soon  kill  them  off,  for  ants  can  combine  and  they  can 
bite  or  sting,  but  they  do  not  think  of  it.  Perhaps  we  make 
an  artificial  problem  by  using  words  like  '  guest '  and  '  host ', 
perhaps  the  truth  is  that  the  crickets  do  not  matter  much 
as  long  as  they  are  not  too  numerous.  Perhaps  and  per- 
haps and  perhaps. 

Ivar  Tragardh  has  described  the  occurrence  of  the  larvae 
of  a  Tineid  moth  in  the  nests  of  a  New  Zealand  termite, 
and  the  story  is  very  quaint.  The  larvae  depend  upon  the 
material  of  the  nest  for  their  food,  and  they  may  be  seen 
moving  along  in  file,  at  regular  intervals  as  if  in  a  procession, 

A  A 


354  THE  WONDER  OF  LIFE 

each  escorted  by  a  few  soldier  and  worker  termites.  It 
appears  that  the  larvse  exude  a  strong  odour  which  is 
attractive  to  the  termites.  Just  as  man  may  have  flowers 
in  a  room  for  the  sake  of  their  perfume,  so  the  termites 
have  caterpillars.  Chacun  d  son  gout. 

In  not  a  few  cases,  the  fact  of  association  is  well  estab- 
lished, but  its  meaning  remains  obscure.  Thus  Mr.  F.  P. 
Smith  has  reported  the  normal  occurrence  of  a  spider 
(Thyreosthenius  biovatus)  in  the  nests  of  the  wood-ant 
(Formica  rufa).  The  ants  tolerate  their  guest,  which  they 
could  readily  destroy,  but  what  the  spider  is  after  remains 
undiscovered.  It  is  possible  that  it  feeds  on  other  inmates 
of  the  ant-hill  (the  scavengers  and  pets)  ;  it  is  possible  that 
it  eats  the  '  ants'  eggs '  on  the  sly.  There  are  two  other 
so-called  '  myrmecophilous  spiders '  in  Britain — on  quite 
a  different  footing  from  spiders  found  casually  wandering 
about  on  ant  hills — but  the  significance  of  the  association 
requires  to  be  looked  into. 

Slave -Making. — If  slave-keeping  among  ants  occurred 
once  or  twice,  one  might  think  it  was  some  strange  aberra- 
tion among  the  little  people,  but  there  are  many  instances 
and  many  stages  of  the  'institution'. 

A  fertilized  queen  of  the  red  ant,  Formica  sanguinea, 
may  fall  after  her  nuptial  flight  into  a  nest  of  black  ants, 
Formica  fusca,  where  there  is  no  queen.  She  is  received 
and  fed,  and  the  eggs  which  she  lays  are  tended.  A  mixed 
colony  arises,  with  the  reds  as  masters  and  the  blacks  as 
slaves,  the  former  being  more  active  in  external  operations 
and  the  latter  in  the  discharge  of  domestic  duties.  As 
the  blacks  do  not  multiply,  the  reds  make  sallies  and  bring 
back  pupae  from  neighbouring  nests  of  blacks.  Those 
that  are  not  eaten  grow  up  to  slavery.  Sometimes,  how- 


THE  WEB   OF  LIFE  355 

ever,  the  slaves  gradually  decrease  in  number,  and  the 
mixed  colony  becomes  a  pure  red  colony.  In  this  case, 
therefore,  the  slave-keeping  need  not  be  more  than  tempor- 
ary. In  fact,  Prof.  Wheeler  has  shown  that  the  largest 
American  colonies  of  Formica  sanguinea  are  very  often 
pure. 

In  the  Amazon  ants  (e.g.  Polyergus  rufescens  in  Europe 
and  P.  lucidus  in  America)  the  '  institution  of  slavery  '  has 
developed,  and  there  are  probably  no  slaveless  colonies. 
A  fertilized  queen  is  accepted  by  some  queenless  colony  of 
Formica  fusca  or  F.  rufibarbis  ;  her  offspring  are  tended 
and  become  dominant ;  and  the  number  of  slaves  is  sus- 
tained or  increased  by  slave-capturing  raids.  Forel  calcu- 
lated that  a  single  colony  may  capture  in  the  course  of 
one  summer  as  many  as  forty  thousand  larvae  and  pupae  of 
slaves — who  grow  up  to  do  everything  for  their  masters, 
just  as  if  these  were  their  own  kith  and  kin.  For  the 
Amazons  can  do  nothing  but  raid ;  their  mandibles  have 
become  sabres  quite  unsuited  for  humble  toil ;  they  cannot 
dig,  but  to  beg  they  are  not  ashamed.  Dr.  Louis  Dublin, 
to  whose  interesting  paper  on  this  subject  we  acknow- 
ledge our  great  indebtedness,  writes  : — 

"  It  has  been  most  clearly  shown  by  many  observers 
that,  if  left  for  as  short  a  period  as  two  or  three  days  with- 
out the  aid  of  their  slaves  they  would  starve  to  death, 
even  if  surrounded  with  an  abundance  of  food.  Replace 
the  black  ants  and  the  scene  changes  immediately ;  the 
Amazons  take  new  courage  and  are  soon  fed  with  the 
regurgitated  food  which  the  slaves  are  only  too  eager  to 
offer  them." 

In  a  sense,  then,  the  tables  have  been  turned,  and  the 
slaves  are  the  masters.  The  Amazons  fight  and  reproduce, 


356  THE  WONDER  OF  LIFE 

but  the  slaves  '  determine  the  character  of  the  nest,  plan 
and  conduct  migrations,  carrying  the  Amazons  from  place 
to  place,  the  latter  subject  to  no  impulse  of  their  own. 
...  In  America  this  once  widely  distributed  species  is 
on  the  road  to  extinction '. 

The  next  stage,  as  indicated  by  Dr.  Dublin,  is  that  pre- 
sented by  a  light  red  European  ant  of  considerable  size, 
Strongylognaihus  testaceus,  and  an  active  well-organized 
little  form,  Tetramorium  caespitum.  The  large  slave- 
makers  have  prominent  sabre-like  mandibles,  but  they  are 
too  delicate  to  do  injury.  They  are  mock  soldiers,  there  are 
relatively  few  of  them,  and  there  are  no  workers. 

There  are  males  and  females  amongst  them,  and  so  there 
are  among  the  '  slaves  '  as  well.  It  is  possible  that  this 
kind  of  mixed  community  has  arisen  by  an  alliance  of  two 
distinct  colonies,  and  that  the  Tetramorium- workers  some- 
how fall  under  the  spell  of  the  Strongylognaihus  males 
and  females,  who  are  absolutely  dependent  upon  them. 

The  final  stage  of  dependence  of  one  species  upon  an- 
other is  represented  by  the  European  Anergates  and  by 
two  American  forms,  Epoecus  pergandei  and  Epipheidole 
inquilina,  in  which  there  are  no  workers  or  soldiers,  but 
simply  males  and  females.  In  Anergates  the  males  are 
wingless  and  both  sexes  are  degenerate ;  they  depend  on 
the  charity  of  small  groups  of  queenless  and  aged  workers 
of  the  Tetramorium  caespitum  species.  This  state  of 
affairs  seems  almost  incomprehensible,  for  it  must  come  to 
an  end  with  the  death  of  the  aged  slaves.  Dr.  Dublin  sug- 
gests that  when  this  occurs  a  winged  female  of  Anergates 
must  seek  out  another  colony  of  Tetramorium  to  adopt 
her. 

The  problem  ofAthe  origin  of  the  slave-making  is  very 


THE  WEB  OF  LIFE  357 

difficult.  Darwin's  suggestion  was  that  many  ants  cap- 
ture the  pupa3  of  other  ants  for  food,  that  some  of  the  stored 
pupse  might  be  unintentionally  reared,  that  if  their  pres- 
ence in  the  community  was  not  resented  but  proved  use- 
ful, the  slave-making  habit  might  gain  ground.  '  If  it 
were  more  advantageous  to  this  species  to  capture 
workers  than  to  procreate  them,  the  habit  of  collecting 
pupse,  originally  for  food,  might  by  natural  selection  be 
strengthened  and  rendered  permanent  for  the  very  differ- 
ent purpose  of  raising  slaves '. 

Dr.  Dublin  makes  a  supplementary  suggestion,  that  we 
must  start  from  the  adoption  of  the  newly  fertilized  queen 
of  the  slave-makers  by  the  workers  of  an  impoverished 
and  queenless  colony.  He  refers  to  Santschi's  observations 
on  a  Tunisian  ant,  Bothriomyrmex,  which  temporarily  en- 
slaves the  workers  of  a  species  of  Tapinoma.  The  young 
queen  B  was  taken  into  the  nest  T,  where  aided  or  unaided 
she  killed  the  queen  T,  and  proceeded  to  lay  eggs.  The 
workers  of  T  reared  the  larvse  of  B,  but  as  the  slaves  died 
off  the  community  became  pure  B  and  self-sustaining. 
If  the  ranks  of  the  slaves  had  been  recruited  by  plundering 
neighbouring  colonies,  then  slave-making  might  have  been 
established.  If  therefore  we  take  together  the  tendency  of 
the  young  queen  to  enter  an  established  nest,  the  tendency 
some  kinds  of  workers  show  to  welcome  a  young  queen 
foreign  to  their  race,  and  the  common  habit  of  capturing 
the  pupae  of  other  species,  we  have  a  basis  for  understanding 
slave-keeping. 

Man  and  the  Web  of  Life . — We  must  end  this  chapter, 
as  we  began  it,  by  emphasizing  the  practical  importance 
of  the  conception  of  the  web  of  life.  In  securing  his 
own  welfare  and  that  of  his  stock  Man  must  keep  the 


358  THE  WONDER  OF  LIFE 

idea  of  subtle  inter-relations  continually  in  view.  It  is 
at  his  peril  that  he  ignores  the  idea.  All  interferences 
with  the  system  of  Nature — notably  exterminations  and 
new  introductions — must  be  sternly  criticized.  Even  the 
conservation  or  favouring  of  one  set  of  organisms  by  arti- 
ficial means  may  be  fraught  with  danger.  We  shall  give 
a  few  instances  of  how  the  circles  intersect. 

The  multitudinous  economic  relations  between  animals 
and  man  have  been  clearly  classified  by  Sir  Ray  Lankester 
in  a  preface  to  a  British  Museum  Report  on  Economic 
Zoology  (1903)  :— 

A.  Captured  or  slaughtered  for  food  and  other  products, 
e.g.  animals  of  the  chase,  food-fishes,  whales,  pearl-oysters. 

B.  Bred,  or  cultivated  for  food  and  other  products,  or 
for  service,  e.g.  flocks  and  herds,  horses,  dogs,  poultry, 
bees,  silkworms,  leeches. 

C.  Promoting   operations   of   civilized  man,   but   not 
by  being  killed,   captured  or    trained,   e.g.    scavengers, 
like    vultures ;     burying    beetles ;     earthworms,    flower- 
pollinating  insects. 

D.  Causing  bodily  injury,    death,   disease,   e.g.   lions, 
wolves,  snakes,  stinging  insects,  germ-carriers  like  flies, 
parasitic  worms,  etc. 

E.  Injuring  man's  domestic  animals,  cultivated  plants, 
or  wild  forms  important  to  him,  e.g.  as  in   D,  but   also 
injurious  insects,  pests  like  voles. 

F.  Injurious  to  man's  worked-up  products  of  art  and 
industry,    such   as   buildings,    furniture,    books,    clothes, 
food   and   stores,    e.g.,    white   ants,    wood-eating   larvae, 
clothes'  moths,  weevils,  ship- worms. 

G.  Beneficial  in  checking  the  increase  of  J>,  E,  F,  e.g. 
certain  carnivorous  and  insectivorous  birds,  reptiles,  and 
amphibians  ;  some  parasitic  and  predaceous  insects. 


THE  WEB  OF  LIFE  359 

That  the  web  of  inter-relations  includes  human  interests 
may  be  illustrated  by  reference  to  the  role  of  birds  in 
preserving  the  balance  of  Nature.  All  other  life  depends  on 
plant  life ;  but  the  great  check  on  plant  life  is  that  of 
insect  life — overwhelming  in  numbers,  overmastering  in 
devices,  and  appalling  in  voracity ;  and  the  great  check 
on  insect  life  is  bird  life — and,  luckily  for  us,  this  again  is 
abundant,  alert,  and  well  appetized.  It  is  very  interesting 
that  the  two  great  classes  of  successful  fliers  should  be 
thus,  in  the  wide  economics  of  Nature,  pitted  against  one 
another,  wings  against  wings,  freeman  against  freeman, 
Invertebrate  against  Vertebrate,  '  little  brain '  against 
'  big  brain,'  '  instinct '  against  '  intelligence.'  Practically 
this  is  the  most  important  conflict  of  classes  that  the 
world  knows. 

There  is  a  biological  suggestiveness  in  the  old  saying 
about  the  dead  flies  which  spoil  the  ointment  of  the  apothe- 
cary, but  it  was  not  till  quite  recently  that  the  important 
role  of  flies  as  disease- disseminators  was  discovered. 
Perhaps  it  was  at  the  time  of  the  Spanish- American  war 
that  it  began  to  be  clearly  recognized  that  the  house-fly 
was  a  carrier  of  enteric  fever  and  therefore  full  of  menace. 
It  is  now  generally  recognized  that  the  house-fly  can  scatter 
the  germs  not  only  of  enteric,  but  of  typhoid  fever  and  of 
cholera,  and  perhaps  of  other  diseases  as  well,  such  as 
infantile  diarrhoea.  It  is  also  known  to  carry  the  tubercle 
bacillus.  Wherever  there  is  a  breeding  ground,  e.g. 
about  a  heap  of  stable  manure,  and  the  possibility  of 
contamination  with  disease-germs,  the  house-fly  becomes 
a  most  serious  danger  as  a  disseminator.  What  is  true  for 
Britain  is  not  less  true  for  the  United  States,  as  Dr.  L.  0. 
Howard  has  proved  up  to  the  hilt. 


360  THE  WONDER  OF  LIFE 

The  carrying  is  twofold,  external  and  internal.  After 
it  has  been  feeding  on  highly  infective  substances,  the  fly 
must  have  many  germs  about  its  legs  and  mouth-parts  and 
body,  and  it  may  readily  implant  these  in  human  food, 
But  its  food-canal  is  also  charged  with  concentrated 
infective  material,  which  may  be  dropped  on  food,  on 
dishes — anywhere.  Professor  Nuttall  remarks  that  "  in 
potential  possibilities  the  droppings  of  one  fly  may,  in 
certain  circumstances,  weigh  in  the  balance  as  against 
buckets  of  water  or  of  milk '. 

Dr.  Gordon  Hewitt  cites  some  important  experiments 
made  by  Giissow,  who  allowed  a  house-fly  (Musca  domestica), 
caught  in  the  room  of  a  house,  to  walk  over  a  culture  plate 
of  agar-agar.  He  obtained  thirty  colonies  comprising 
six  species  of  bacteria  and  six  colonies  comprising  four 
species  of  fungi.  From  another,  caught  in  the  open,  he 
obtained  forty- six  colonies  comprising  eight  species  of 
bacteria  and  seven  colonies  comprising  four  species  of 
fungi.  "  The  tracks  of  a  house-fly  caught  in  a  household 
dustbin  yielded  116  colonies  of  bacteria  comprising  eleven 
species,  and  including  such  species  as  Bacillus  coli,  B. 
lactis  acidi,  and  Sarcina  ventriculi,  and  ten  colonies  com- 
prising six  species  of  fungi'.  A  very  important  fact, 
proved  by  Faichne,  is  that  if  the  maggot  stage  be  de- 
veloped in  infected  typhoid  material,  then  the  fly  has  also 
typhoid  bacilli  in  its  alimentary  canal. 

It  might  seem  to  the  uninitiated  a  sad  waste  of  time  to 
inquire  into  the  House  Fly's  flying  capacities.  But  it  is 
a  very  important  practical  question,  for  the  range  of  flight 
determines  the  fly's  range  of  mischief.  Dr.  Hindle  finds  that 
house-flies  tend  to  travel  either  against  or  across  the  wind. 
This  direction  may  be  directly  determined  by  the  action  of 


THE  WEB  OF  LIFE  361 

the  wind,  or  indirectly,  owing  to  the  flies  being  attracted 
by  odours  borne  by  the  wind.  Fine  weather  and  warmth 
favour  dispersal,  and  flies  travel  further  in  the  open  country 
than  in  towns,  probably  because  the  houses  offer  food  and 
shelter.  In  thickly  housed  localities  the  usual  maximum 
flight  is  about  a  quarter  of  a  mile,  but  in  one  case  a  single  fly 
was  recovered  at  a  distance  of  770  yards  (partly  over  open 
fen  land).  When  set  free  in  the  afternoon,  flies  do  not 
scatter  so  well  as  in  the  morning.  Liberated  flies  often 
mount  almost  vertically  to  a  height  of  forty-five  feet  or 
more.  Every  detail  of  this  is  important  because  flies  are 
disease-distributors. 

Besides  carrying  the  germs  of  diseases  that  affect  animals, 
flies  may  do  something  in  the  way  of  spreading  the  diseases 
of  plants.  Thus  L.  Mercier  has  noticed  that  a  common 
summer  fly,  Sciara  thomce,  carries  about  the  spores  of 
the  fungus  (Claviceps)  which  causes  ergot  on  rye-grass. 
The  spores  were  abundant  in  the  food- canal  of  the  fly  and 
did  not  seem  to  be  digested  ;  they  also  occurred  on  the 
setse  of  the  body.  Although  it  has  not  been  experimentally 
proved  that  the  flies  infect  healthy  plants  with  Claviceps, 
there  is  no  doubt  that  they  carry  the  germs  and  that  they 
frequent  rye-grass. 

Not  a  few  insects  are  subject  to  fatal  attacks  of  fungoid 
parasites,  and  use  is  now  being  made  of  this  to  further  the 
destruction  of  injurious  pests.  By  artificially  favouring 
the  dissemination  of  the  fungus  it  has  been  found  possible 
to  cause  a  useful  plague  among  the  insects.  Much  good 
has  been  done  in  this  way  in  checking  the  scale  insects 
which  attack  the  limes  in  Dominica  and  Montserrat  and 
similar  islands.  It  has  been  recently  suggested  that  an 
artificial  diffusion  of  a  fungus,  Empusa  muscce,  which  is 


362  THE  WONDER  OF  LIFE 

a  specific  parasite  of  house-flies  and  their  relatives,  may 
be  useful  as  a  check  to  the  multiplication  of  these 
disease-distributors.  One  cannot  help  feeling  that  such 
measures  should  be  backed  up  by  more  evolved 
cleanliness. 

Man  has  in  great  measure  freed  himself  from  the  disgrace 
of  gaol-fever  or  typhus  fever,  the  germs  of  which  used  to 
be  transmitted  from  man  to  man  by  the  clothes-louse, 
and  he  is  in  process  of  conquering  other  plagues,  a 
step  in  the  conquest  being,  in  every  case,  an  investigation 
of  linkages.  Every  one  knows  how  the  minute  animals 
which  cause  malaria  (Plasmodium)  and  sleeping-sickness 
(Trypanosomes)  are  disseminated  respectively  by  the 
mosquito  (Anopheles  maculipennis)  and  the  tse-tse  fly 
(Glossina  palpalis),  and  the  human  importance  of  these 
four  animals  is  beyond  all  estimation. 

A  curious  though  perhaps  unimportant  fact  concerning 
a  near  relative  of  the  Trypanosomes  has  been  recently 
reported,  and  may  serve  to  illustrate  possible  complica- 
tions. A  species  of  Leptomonas  was  discovered  by  Lafont 
in  the  latex  of  Euphorbia  pilulifera  in  Mauritius,  and  this  has 
been  confirmed  by  G-.  Bouet  and  E.  Roubaud  in  regard  to 
other  Euphorbias.  They  regard  the  infection  as  local 
and  temporary  and  without  obvious  pathological  effects. 
There  seems  little  doubt  that  the  plant  is  infected  through 
the  agency  of  a  bug. 

That  rats  have  to  do  with  plague  was  perhaps  referred 
to  in  the  Bible  in  the  account  of  an  epidemic  among  the 
Philistines,  which  they  connected  apparently  with  '  the 
mice  that  marred  the  land '.  In  more  recent  times,  the 
association  of  rat-mortality  and  human-mortality  seems 
to  have  been  often  remarked,  and  regarded  as  more  than  a 


THE   WEB   OF  LIFE 


363 


FIG.  57. — A  common    mosquito,     Anopheles    maculipennis     (female), 
which  carries  the   Protozoon  causing   malaria.     (After  Nuttall.) 

coincidence.  Avicenna  refers  to  it  in  connexion  with  a 
plague  in  Mesopotamia  about  A.D.  1000.  But  the  identity 
of  the  diseases  in  rat  and  man  was  not  established  till 
1894,  when  the  Bacillus  pestis  was  discovered  by  Yersin  and 
Kitasato.  This  bacillus  is  a  minute  rod-like  body  with 
rounded  ends,  about  ^WQ-Q  of  an  inch  in  length.  It  is  fatal 
not  only  to  man,  but  to  rats,  mice,  guinea-pigs,  rabbits, 
hares,  ferrets,  cats,  monkeys,  and  American  ground 


364  THE  WONDER  OF  LIFE 

squirrels.  It  causes  an  acute  fever  associated  with  swellings 
of  the  lymphatic  glands  (bubonic  type),  or  it  may  primarily 
attack  the  lungs  (pneumonic  type),  or  it  may  primarily 
poison  the  blood  (septicsemic  type).  The  '  black  death ' 
which  destroyed  about  a  fourth  of  the  population  of 
Europe  in  the  fourteenth  century  was  apparently  of  the 
pneumonic  type  and  highly  infectious. 

The  microbe  of  plague  (in  its  ordinary  modern  form) 
is  not  effectively  transported  by  wind  or  in  water  or  in 
food.  In  rare  cases  it  might  be  swallowed  by  man,  but  it 
cannot  make  an  effective  entrance  through  the  food  canal. 
It  enters  man  through  the  bite  of  one  of  the  Indian 
rat  fleas  (Pulex  cheopis).  An  outbreak  of  plague  among 
human  beings  in  India  is  preceded  by  an  outbreak  of 
plague  among  the  black  rats  (Mus  rattus)  which  frequent  the 
houses  in  great  numbers.  A  flea  bearing  the  plague  bacilli 
from  the  rat's  blood  bites  man  and  thus  infects  him.  There 
are  other  kinds  of  fleas  on  rats,  but  Pulex  cheopis  is  the  only 
one  which  will  readily  bite  man. 

A  plague  is  known  to  occur  in  the  marmots  or  '  tarba- 
gans  '  of  Manchuria  and  an  analogous  disease  in  those  who 
hunt  the  animal  for  the  sake  of  its  skin.  There  are  very 
large  fleas  on  the  marmot,  and  it  is  possible  that  in  the 
epidemics  of  plague  in  Manchuria  the  marmot-flea  may 
play  the  same  part  as  the  rat- flea  in  India. 

There  have  been  many  hints  lately  that  mites  have  a 
more  complicated  inter-relation  with  man  and  his  domestic 
animals  than  that  which  is  implied  in  their  being  a 
punishment  for  lack  of  cleanliness.  (For  mites  are  always 
trying  to  clean  things  up.)  It  is  probable  that  they  have, 
like  ticks,  a  role  in  the  spreading  of  disease.  It  has  been 
suggested  that  the  very  common  follicle-mite  (Demodex 


THE  WEB  OF  LIFE  365 

folliculorum),  generally  regarded  as  a  trivial  parasite  of  the 
human  skin,  may  pave  the  way  for  some  skin  diseases. 
One  of  the  hints  we  have  alluded  to  is  Dr.  Dahl's  announce- 
ment of  a  new  mite,  Tarsonemus  hominis,  found  by  Dr. 
Saul  in  two  cases  in  a  human  tumour.  Was  it  simply  a 
parasite  in  the  tumour,  or  had  it  a  share  in  causing  the 
growth?  It  is  well  known  that  some  of  the  species  of 
Tarsonemus  cause  gall- like  cell-proliferation  in  plants. 

Yellow  fever,  or  '  yellow  Jack  '  as  it  used  to  be  called,  is 
a  dread  disease  that  used  to  break  out  on  ships  sailing  to 
West  Africa,  the  West  Indies,  and  the  like.  It  has  occa- 
sionally occurred  in  English  and  French  ports,  and  at  times 
severely  in  New  York  and  Philadelphia,  but  it  is  practically 
confined  to  between  latitude  40°  N.  and  S.  and  longitude  20° 
E.  and  100°  W.  The  fell  disease  is  transmitted  by  a 
kind  of  mosquito,  Stegomyia  fasciata,  which  is  almost 
world-wide  between  the  parallels  of  latitude  40°  north 
and  south,  a  fact  of  incalculable  human  importance.  For 
if  the  disease  should  be  introduced  into  the  East,  for  in- 
stance by  the  opening  of  the  Panama  Canal,  Stegomyia 
fasciata  is  there  to  spread  it  disastrously.  Fortunately, 
however,  to  be  forewarned  is  to  be  forearmed,  and  the 
forearming  is  now  feasible  enough.  Since  the  American 
Commission  in  1899  proved  up  to  the  hilt  what  had  been 
previously  suggested,  that  Stegomyia  fasciata  is  the  carrier  of 
the  disease,  the  prevention  of  yellow  fever  has  become 
possible.  The  mosquito  in  question  is  a  '  house-haunting ' 
insect,  and  it  always  breeds  near  dwellings.  The  larvae 
develop  in  artificial  collections  of  stagnant  water,  for 
instance  in  old  pots  and  pans.  If  these  breeding-places 
are  destroyed,  if  the  mosquito  nets  and  screens  are  used, 
and  if  patients  are  screened  and  segregated,  so  that  fresh 


366  THE  WONDER  OF  LIFE 

mosquitos  be  not  infected,  then  Yellow  Jack  is  conquered. 
As  a  matter  of  fact,  the  disease  has  been  quite  stamped  out 
in  Havanna. 

It  comes  to  this,  then,  that  the  great  practical  lesson  of 
Natural  History  is  to  recognize  the  complexity  of  inter- 
relations, '  the  wheels  within  wheels  '.  In  a  report  of  a 
lecture  by  Mr.  James  Buckland,  we  read  :  '  The  destruc- 
tion of  the  white  heron  for  its  scapular  plumes  has  robbed 
half  the  world  of  a  bird  which  is  most  useful  to  man.  Its 
loss  to  India  and  to  China  is  most  serious.  It  never  touches 
grain,  but  feeds  solely  near  water  and  over  damp  ground, 
the  breeding-places  of  innumerable  batrachians,  small 
crustaceans,  and  pestiferous  insects,  all  of  which  directly 
or  indirectly  injuriously  affect  crops  in  the  neighbourhood. 
The  presence  of  the  white  heron  in  the  rice-fields,  for  in- 
stance, is  distinctly  beneficial  to  the  farmer,  and  rice  is 
one  of  the  most  extensively  grown  crops  of  India  and  of 
China.' 

In  this  connexion  it  may  be  useful  to  point  out  that 
many  eliminations  consequent  on  Man's  intrusion  cannot 
be  directly  brought  home  to  him  as  the  results  of  any 
ruthlessness.  Thus  one  of  the  most  extraordinary  of 
recent  disappearances  is  that  of  the  Passenger  Pigeon 
(Ectopistes  migratorius)  which  used  to  breed,  within  the 
memory  of  living  man,  in  huge  numbers  in  the  North 
American  forests.  Wilson,  the  American  ornithologist, 
estimated  a  flock  at  2,230  millions,  and  in  1912  there  was 
said  to  be  only  one  individual  left,  a  female  bird,  about 
nineteen  years  old,  belonging  to  the  Zoological  Society  of 
Cincinnati.  It  is  difficult  to  believe  that  there  are  not 
survivors  in  the  woods,  but  persistent  efforts  to  find  them 
have  not  been  rewarded  with  any  success. 


THE  WEB   OF   LIFE  367 

A  second  point  of  importance  is  that  very  strong  en- 
couragement has  rewarded  many  of  the  endeavours  to 
conserve  life — endeavours  now  happily  on  the  increase. 
Thus  the  three  herds  of  bison  maintained  by  the  Govern- 
ment of  the  United  States  comprised  in  1910  over  150  head, 
and  the  total  of  pure-bred  bisons  living  in  North  America 
was  a  little  over  2,000 — a  satisfactory  result  of  careful 
protection.  Equally  full  of  promise  are  the  records  of 
reserve-areas  and  bird-sanctuaries  (like  those  of  the  Sel- 
borne  Society  in  Britain  and  the  Audubon  Society  in  the 
United  States),  and  of  individual  efforts  (we  think,  for 
instance,  of  Mr.  Ford,  the  well-known  motor-car  manu- 
facturer) to  conserve  what  may  be  fairly  called  vital  assets. 
In  Conclusion. — These  few  instances  must  serve  to  illus- 
trate the  fact  that  animated  Nature  is  a  vast  system  of  link- 
ages and  inter-relations.  No  creature  lives  or  dies  to  itself. 
The  threads  of  one  lif  e  get  caught  up  and  intertwined  with 
those  of  another.  The  liver-fluke  of  the  sheep  cannot  get 
on  without  the  water- snail,  nor  the  bitterling  without  the 
freshwater  mussel,  nor  the  mussel  without  the  minnow, 
or  some  such  fish,  nor  the  clover  without  the  bee.  We  find 
these  inter-relations  in  all  degrees  of  perfection,  some  old 
established  and  working  smoothly,  others  in  the  making  or 
on  trial,  and  others  again  apparently  making  for  the  ex- 
tinction of  one  at  least  of  the  associates.  But  in  whatever 
stage  of  evolution  they  are,  their  interest  is  great,  the 
web  of  life  is  a  great  fact  in  Nature,  and  it  is  one  of  the 
naturalist's  delights  and  tasks  to  discern  the  threads. 

The  general  idea  we  have  been  expounding  was  tersely 
put  in  an  address  by  Dr.  T.  Muir.  '  The  specialist  must 
aim  a  little  more  at  width  of  outlook  and  knowledge  of  men 
and  affairs,  must  seek  to  moderate  his  exaggerated  estimate 


368  THE  WONDER  OF  LIFE 

of  the  importance  of  his  own  little  domain,  and  must  try 
to  see  good  in  the  labours  of  other  specialists  in  fields  far 
distant  from  his  own,  never  forgetting  that  all  fields  are 
but  perfectly  fitted  portions  of  a  cosmic  whole,  and  that, 
as  the  botanist  and  the  astronomer  in  particular  must 
come  to  know — 

'  Thou  canst  not  stir  a  flower, 
Without  troubling  a  star '. 

When  we  think  quietly  over  the  extraordinary  series 
of  facts  brought  together  in  this  chapter — which  is  but 
one  of  a  possible  thousand  and  one  nights  of  tales — we 
confess  to  a  feeling  of  wonder.  Life  overwhelms  us  with 
its  subtlety  of  linkage. 

'  We  recognize,  of  course,  that  many  haunts  of  life  are 
densely  crowded,  and  commoner  rubs  elbow  with  patrician 
in  the  throng  of  the  streets,  but  the  wonder  is  the  intimate 
interlinking  of  life  with  life.  Contact  is  nothing,  it  is  the 
correlation  that  impresses  us.  Flowers  and  their  visitors 
fit  one  another  as  glove  and  hand  ;  cats  influence  the  clover 
crop  and  the  incidence  of  the  plague  in  Indian  villages ; 
water- wagtails  have  to  do  with  the  success  of  sheep-farming, 
and  mosquitoes  with  the  decadence  of  Greece. 

This  is  one  of  the  big  facts  of  life,  the  correlation  of 
organisms;  and,  to  our  thinking,  its  deep  significance 
is  twofold.  On  the  one  hand,  it  seems  congruent  with  the 
deep-seated  tendency  of  Nature  to  complexity.  It  looks 
as  if  a  story  were  being  told.  For  there  is  reason  to  believe 
that  in  the  course  of  time  atoms  became  molecules,  and 
molecules  larger  molecules,  and  these  colloidal  masses.  It 
is  conceivable  that  these  incorporated  partner  molecules 
and  became  protoplasm  ;  and  that,  by  and  by,  viable  units 
of -protoplasm,  to  wit,  living  creatures,  emerged,  and  a  world 


THE  WEB  OF   LIFE  369 

of  life  began.  Our  hypothesis,  based  on  many  facts,  is 
that  in  this  new  world  of  life  the  complexifying  tendency 
continued,  and  we  call  that  the  self-differentiation  of 
protoplasm.  Living  creatures  traded  with  time  and  found 
fuller  and  fuller  self-expression.  No  one  doubts  that  many 
kinds  of  '  flesh '  originated,  one  kind  of  fishes,  another  of 
birds,  another  of  beasts,  another  of  man,  as  was  said  in 
olden  time. 

But  we  must  add  to  this  or  superimpose  on  it  another 
idea,  that  the  living  creature  is  associative.  We  do  not 
wish  to  multiply  formulse  or  mysterious  tendencies,  but 
there  seems  to  be  a  touch  of  protoplasm  that  makes  diverse 
creatures  kin.  A  quaint  instance  may  serve  as  a  diagram. 
In  recently  examining  at  Roscoff  a  large  collection  of  the 
little  green  worms  known  as  Convoluta  roscoffensis,  Marcel 
A.  Herubel  found  among  them  about  forty  specimens  of 
Convoluta  flavibacillum,  a  species  which  is  not  green,  which 
had  not  been  previously  noticed  in  this  locality.  The 
peculiar  fact  was  observed,  that  on  the  ventral  surface  of 
each  of  them  there  was  a  young  C.  roscoffensis,  clinging 
on  by  its  dorsal  surface.  When  they  wrere  separated 
in  the  aquarium,  they  were  re-united  in  half  an  hour ! 
The  meaning  of  the  peculiar  association  remains  quite 
obscure,  but,  whatever  it  may  be,  the  case  may  serve  to 
illustrate  our  idea,  that  many  organisms  go  about  with, 
as  it  were,  tendrils  Unking  themselves  on  to  other  organisms. 
We  have  no  great  faith  in  the  multiplication  of  '  tropisms  ', 
or  inherent  predispositions  of  organisms  to  move  on  certain 
ways  in  answer  to  precise  stimuli,  but  we  would  suggest 
an  addition  to  the  list,  viz.  '  biotropism  ' — the  attraction 
of  organism  to  organism.  To  rank  this  beside  '  geotropism  ', 
'  heliotropism  ',  '  thigmotropism  ',  '  chemotropism  ',  and 

BB 


370  THE  WONDER  OF  LIFE 

the  like  will  not  indeed  make  occurrences  any  clearer, 
but  it  may  serve  as  a  useful  labelled  string  for  a  large  series 
of  facts — the  linking  of  one  organism  to  another,  at  points 
where  their  lines  of  life  intersect,  although  we  often  cannot 
see  any  obvious  reason  why  they  should  do  so.  After 
the  event,  we  say,  *  It  pays ' ;  but  who  could  have  pre- 
dicted its  success.  In  any  case,  the  correlation  of  organ- 
isms in  the  web  of  life  is  a  large  fact.  Nature  continues 
to  complexify  her  system. 


CHAPTER  VI 

THE  CYCLE  OF  LIFE 
(FROM  BIRTH  THROUGH  LOVE  TO  DEATH) 


instant  sbe  commences  an  immense  journey,  ano 
everg  instant  sbe  bas  reacbeo  bee  goal  '.  '1foer  life  is  in  ber 
cbfloren'  ....  "Iber  cbiloren  are  numberless'.  .  .  .  *1ber 
crown  is  love  '.  .  .  .  ^©ver  greatness  sbe  spreads  ber 
sbfelo'.  .  .  .  *  2>eatb  is  ber  expert  Device  to  get  plenty  of  life'. 

—  Goethe's  Aphorisms,  translated  by  Huxley. 

The  Curve  of  Life—  The  Continuance  of  Life—  The  Wonder  of 
Development  —  Growth  —  Young  Animals  —  Adolescence  —  Court- 
ship among  Animals  —  Parental  Care  and  the  Family  —  Ageing 
and  Senescence  —  Death  —  Illustrations  of  Life-histories  —  The 
Story  of  Niners. 

THE  living  creature  is  always  changing  in  its  material 
composition,  yet  it  has  a  remarkable  power  of 
retaining  its  integrity.  This  is  one  of  its  secrets.  It  burns, 
but  is  not  consumed.  Besides  this,  however,  it  has  the 
power  of  passing  from  form  to  form,  from  phase  to  phase  — 
the  power  of  '  cyclical  development  ',  as  Huxley  called  it. 
This  is  our  main  theme  in  this  chapter. 

The  Curve  of  Life.  —  From  a  microscopic  egg-cell, 
hidden  within  the  ovule,  fertilized  by  a  pollen-nucleus, 
an  embryo  plant  develops  ;  the  seed  is  sown  and  a  seedling 
develops  ;  the  seedling  becomes  a  sapling  ;  this  grows  into 
a  tree  which  bears  flowers  and  seeds  year  after  year,  it 
371 


372  THE  WONDER  OF  LIFE 

may  be  for  centuries,  but  finally  becomes  old,  decays  and 
dies,  falling  to  the  ground,  '  dry,  bald  and  sere '. 

Speaking  of  the  beanstalk  developing  from  the  bean, 
Huxley  wrote : 

'  By  insensible  steps,  the  plant  builds  itself  up  into  a 
large  and  various  fabric  of  root,  stem,  leaves,  flowers, 
and  fruit,  every  one  moulded  within  and  without  in  accord- 
ance with  an  extremely  complex,  but,  at  the  same  time, 
minutely  denned  pattern.  In  each  of  these  complicated 
structures,  as  in  their  smallest  constituents,  there  is  an 
immanent  energy,  which,  in  harmony  with  that  resident 
in  all  the  others,  incessantly  works  toward  the  maintenance 
of  the  whole  and  the  efficient  performance  of  the  part  it 
has  to  play  in  the  economy  of  nature.  But  no  sooner  has 
the  edifice,  reared  with  such  exact  elaboration,  attained 
completeness,  than  it  begins  to  crumble.  By  degrees,  the 
plant  withers  and  disappears  from  view,  leaving  behind 
more  or  few  apparently  inert  and  simple  bodies,  just  like 
the  bean  from  which  it  sprang  ;  and  like  it  endowed  with 
the  potentiality  of  giving  rise  to  a  similar  cycle  of  mani- 
festations'.  .  .  .  It  is  a  '  Sisyphsean  process,  in  the  course 
of  which  the  living  and  growing  plant  passes  from  the 
relative  simplicity  and  latent  potentiality  of  the  seed  to 
the  full  epiphany  of  a  highly  differentiated  type,  thence 
to  fall  back  to  simplicity  and  potentiality '  (Evolution 
and  Ethics,  1893). 

The  life-cycle  is  even  more  striking  among  animals. 
The  fertilized  egg-cell  divides  and  redivides  ;  the  segmen- 
tation-cells are  arranged  and  differentiated ;  an  embryo 
is  formed,  which  goes  on  developing,  directly  or  circuitously, 
until  the  result  is  a  reproduction  of  the  parent  organism. 
But  when  the  ascent  from  a  vita  minima  at  the  start  has 
reached  the  vita  maxima  of  maturity,  there  begins  to  be  a 


THE  CYCLE  OF  LIFE  373 

reversal  of  the  process.  There  is  a  quick  or  slow  descent 
to  the  vita  minima  of  senescence,  ending  in  natural  death, 
if  violent  death  has  not  previously  intervened.  Varied 
as  the  life-histories  are,  there  is  always  the  same  general 
phenomenon  of  cyclical  development. 

The  shape  of  the  curve  differs  greatly  in  different  types. 
Some  have  a  short  youth,  e.g.  Aphides ,  which  are  almost 
like  adults  at  birth  and  set  to  work  at  once  ;  while  others 
have  a  long  youth,  e.g.  frogs,  which  spend  about  three 
months  in  the  larval  state.  Some  have  a  prolonged 
maturity,  e.g.  most  birds  and  mammals  ;  while  others  have 
it  soon  cut  short,  e.g.  May-flies,  which  are  sometimes 
literally  insects  of  a  day.  There  may  be  prolonged  adoles- 
cence, as  in  an  eel,  or  a  precocious  maturity,  as  in  a  rat. 
Two  general  ideas  should  be  borne  in  mind  (a)  that  life- 
histories  differ  from  one  another  in  the  lengthening  out 
or  shortening  down  (sometimes  even  telescoping)  of  parti- 
cular periods ;  and  (6)  that  they  differ  much  more  inti- 
mately in  the  details  of  the  curve — in  the  minor  ups  and 
downs — which  mark  the  vicissitudes  of  days  and  seasons, 
and  the  often  correlated  internal  periodicities. 

The  Continuance  of  Life. — A  chronometer  well- wound 
can  keep  agoing  for  a  long  time,  but  it  eventually  comes 
to  a  standstill,  and  so  does  the  organism.  An  intricate 
device  like  the  famous  Strassburg  clock  may  go  through 
a  complicated  performance,  with  processions  of  figures 
and  the  like,  but  eventually  the  mechanism  runs  down 
and  the  show  is  over.  So  is  it  with  the  organism.  But 
there  are  several  big  differences  between  an  organism  and 
a  mechanism,  and  one  is  that  the  organism  normally 
gives  origin  to  other  organisms  like  itself  or  shares  in  so 
doing.  It  multiplies  or  reproduces  itself. 


374  THE  WONDER  OF  LIFE 

Thus  the  life  of  the  organism  is  very  different  from  the 
path  of  a  rocket  in  the  air,  which  spends  itself  wholly  in 
its  brilliant  career,  for  normally  the  organism  has  offspring. 
The  vital  trajectory  is  different  from  the  course  of  the 
drops  of  water  in  a  fountain,  which  rise  to  the  summit, 
sparkle  a  moment  in  the  sunlight,  and  sink  again  to  earth. 
The  organism  secures  the  continuance  of  its  kind. 

The  Wonder  of  Development. — There  are  some 
beautifully  transparent  eggs  which  we  can  watch  as  they 
develop,  actually  witnessing  the  divisions  and  displace- 
ments of  cells.  The  egg  of  one  of  the  moths,  Botys 
hiemalis,  is  a  good  illustration,  and  there  are  few  pro- 
cesses that  go  on  in  the  world  more  impressive  than  this 
development — the  emergence  of  the  obviously  complex 
from  the  apparently  simple.  In  the  case  of  the  hen's 
egg,  that  we  are  so  familiar  with,  a  small  drop  of 
transparent  living  matter  lies  like  an  inverted  watch- 
glass  on  the  top  of  the  ball  of  yolk.  From  that  drop,  in 
the  course  of  three  weeks,  the  chick  is  built  up — the  most 
familiar  fact  in  the  world  and  surely  wonderful.  In  his 
forty-ninth  Exercitation  on  '  the  efficient  cause  of  the 
chicken,'  Harvey  quaintly  expressed  his  sense  of  the 
wonder : — 

'  Although  it  be  a  known  thing  subscribed  by  all,  that 
the  foetus  assumes  its  original  and  birth  from  the  male 
and  female,  and  consequently  that  the  egge  is  produced 
by  the  cock  and  henne,  and  the  chicken  out  of  the  egge,  yet 
neither  the  school  of  physicians  nor  Aristotle's  discerning 
brain  have  disclosed  the  manner  how  the  cock  and  its  seed 
doth  mint  and  coine  the  chicken  out  of  the  egge.' 

Development  is  the  '  becoming '  of  the  individual 
organism.  It  is  the  attainment  of  a  specific  form  and 


THE  CYCLE  OF  LIFE 


375 


structure,  and 
of  the  not  less 
characteristic 
associated 
faculties  or 
activities. 
Often  we  can- 
not tell  one 
kind  of  egg 
from  another, 
but  the  one 
will  develop 


FIG.  58. — Egg  of  Ascidian,  Ciona  intestinalis,  after 
Duesberg,  to  show  distribution  of  organ- 
forming  substances  in  the  egg,  which  is 
about  to  divide  into  two.  At  the  lower 
pole  there  is  a  distinct  crescent  with  very 
crowded  small  granules  (plastochondria) ; 
around  the  division-spindle  in  the  centre 
there  is  a  clear  zone  ;  the  upper  portion  of 
the  egg  has  numerous  yolk  granules  and 
few  plastochondria. 


into  a  star- 
fish and  the 
other  into  a 
sea-urchin, 
one  will  be- 
come a  rep- 
tile and  the 

other  a  bird.     Development  is  the  expression  or  realization 
of  an  inheritance. 

The  starting-point  of  an  individual  life  is  usually  a 
fertilized  egg-cell — a  new  unity  formed  by  the  intimate 
and  orderly  union  of  paternal  and  maternal  inheritances, 
conveyed  we  know  not  how  in  the  often  microscopic  egg- 
cell  and  the  extremely  microscopic  sperm- cell.  There 
may  be  development  from  a  bud  or  from  a  fragment  of  a 
parent  organism — this  is  the  expensive  process  of  asexual 
reproduction.  There  are  also  many  cases  of  partheno- 
genesis, where  the  egg-cell  develops  without  being  ferti- 
lized. Thus  a  drone-bee  has  a  mother  but  no  father,  but 
these  modes  of  asexual  reproduction  and  parthenogenetic 


376  THE  WONDER  OF  LIFE 

development  are  relatively  exceptional,  and  the  individual's 
start  in  life  is  usually  the  fertilized  egg- cell. 

The  fertilized  ovum  divides  and  redivides,  and  we  may 
see  this  going  on  in  the  frog's  spawn  in  the  ditch.  In  that 
case  a  groove  appears  dividing  the  ovum  into  a  right  and 
left  cell ;  then  another,  at  right  angles  to  the  first,  dividing 
each  of  these  into  an  anterior  and  a  posterior  half  ;  then  a 
third  cleavage  in  a  horizontal  plane  cuts  the  four  cells  across 
the  equator,  forming  an  upper  hemisphere  with  four 
smaller,  and  a  lower  hemisphere  with  four  larger  cells.  In 
some  cases  the  process  of  cleavage  suggests  the  operation 
of  an  invisible  magical  knife. 

For  a  time  the  process  of  division  continues  without 
there  being  any  growth,  and  a  ball  of  cells  (or  blastomeres) 
is  formed  which  is  still  no  larger  than  the  original  unseg- 
mented  ovum.  But  growth  soon  begins,  and  the  cells 
are  arranged  in  germinal  layers,  or  are  variously  localized 
by  processes  of  infolding  and  overlap.  Sooner  or  later 
the  cells  begin  to  show  differentiation,  some  laying  the 
foundations  of  the  nervous  system,  others  of  the  muscular 
system,  others  of  the  digestive  system,  and  so  on.  And 
besides  differentiation  there  is  the  process  of  integration 
— the  unification  and  co-ordination  of  the  developing 
organism.  In  short,  there  is  a  process  of  embryonic 
development — condensing  into  a  few  days  or  weeks  the 
achievements  of  ages  of  evolution. 

At  a  certain  stage,  differing  greatly  in  the  different  types, 
the  egg  is  '  hatched ',  and  there  emerges  from  the  egg- 
envelope — a  young  creature  which  is  a  delightful  miniature 
of  the  adult,  as  in  the  familiar  case  of  a  chick,  or  a  larva 
very  different  from  the  adult,  as  in  the  case  of  caterpillar 
and  tadpole.  The  embryo  is  the  quiescent  stage  within 


O 


FIG.  58A. — Segmentation  of  the  egg  of  African  Clawed  Toad,  Xenopus  laevis.  I. 
The  unfertilized  egg  with  pigment  and  the  nucleus  in  its  upper  hemisphere. 
II.  The  8-cell  stage,  seen  from  below.  III.  The  early  blastula  or  '  ball  of  cells ' 
stage.  (After  E.  J.  Bles.) 


THE   CYCLE  OF  LIFE  377 

the  egg-membrane  ;  the  larva  is  free-living  and  able  to  feed 
for  itself ;  but  the  larval  stage  may  be  suppressed,  and 
then  we  say  that  out  of  the  egg-envelope  there  emerges  a 
young  creature.  Thus  in  one  type  the  embryonic  develop- 
ment is  succeeded  by  a  long  larval  period,  while  in  another 
type  the  embryonic  development  eventuates  in  a  young 
creature  like  a  miniature  of  the  parent. 

It  is  very  difficult  to  discover  a  quite  satisfactory  punctu- 
ation of  life — to  say  for  instance  when  development  stops. 
As  long  as  the  expression  of  the  inheritance  goes  on,  as 
long  as  differentiation  and  integration  continue,  we  may 
certainly  speak  of  development,  but  mere  increase  in  size 
is  not  development,  and  it  is  very  difficult  to  know  when 
to  put  in  the  stop.  Some  would  say  that  there  is  no  stop 
at  all  until  death,  and  that  development  includes  all  the 
normal  changes  of  form  and  structure  that  occur  through- 
out life,  the  breaking  down  in  old  age  being  on  this  view 
just  as  much  part  of  development  as  the  building-up  of 
youth.  This  usage  seems  more  logical  than  useful,  for 
the  changes  of  senescence  are  for  the  most  part  of  the 
nature  of  '  involution  '  rather  than  of  evolution. 

Others  would  put  in  the  stop  when  the  limit  of  growth 
is  reached,  but  the  brain  may  go  on  developing  long  after 
that,  though  in  mammals  there  seems  to  be  no  increase 
in  the  actual  number  of  brain-cells  after  birth.  Moreover, 
as  we  have  seen,  there  are  many  fishes  and  reptiles  that 
show  no  limit  of  growth. 

Others  would  put  in  the  stop  when  the  specific  characters 
are  well-defined,  when  the  creature  has  put  on  the  dress 
that  is  its  own  and  no  other's.  There  seems  a  great  deal 
to  be  said  for  this  punctuation,  but  it  is  open  to  the  ob- 
jection of  excluding  much  that  can  be  justly  called  develop- 


378  THE  WONDER  OF  LIFE 

ment,  e.g.  the  changes  associated  with  sexual  maturity. 
The  fact  is  that,  in  studying  development,  we  are  considering 
the  living  creature  in  its  time-relations,  and  definition 
is  a  matter  of  convenience. 

The  first  wonder  of  development  is  the  minuteness  of  the 
starting-point.  Even  when  we  use  the  comfortable  word 
potentiality,  we  find  it  difficult  to  deny  the  wonder  of  con- 
densing a  complex  inheritance  into  a  microscopic  germ-cell. 
An  ovum  the  size  of  a  pin's  head  is  a  large  ovum,  as  ova  go. 
Many  are  microscopic,  and  a  spermatozoon  may  be  only 
fwoooth  °f  *ne  ovum's  size.  Can  there  be  room  in  these 
minute  vehicles  for  the  complexity  of  organization  which 
an  inheritance  implies  ? 

The  wonder  grows  when  we  consider  some  of  the  facts 
of  modern  embryological  research.  Prof.  Delage  cut  the 
very  minute  egg  of  a  sea-urchin  into  three  parts,  and  reared 
a  larva  from  each  of  them.  In  another  case  he  reared  an 
embryo  from  sVth  of  a  sea-urchin's  egg.  Twin  animals 
may  often  be  obtained  from  one  ovum  by  producing  a 
separation  of  the  first  two  cleavage-cells.  Professor  E. 
B.  Wilson  produced  quadruplets  by  shaking  apart  the 
four-cell  stage  in  the  development  of  the  lancelet. 

The  second  wonder  is  germinal  continuity.  These 
germ-cells  are  not  ordinary  cells  ;  they  are  like  the  fertilized 
ovum  which  gave  rise  to  the  parent.  All  the  cells  of  the 
body  are  continuous  with  the  original  fertilized  ovum  by  a 
succession  of  cell-divisions,  but  in  the  case  of  the  germ-cells 
the  lineage  is  undifTerentiated.  In  many  cases,  scattered 
throughout  the  animal  kingdom,  from  worms  to  fishes, 
the  beginning  of  the  lineage  of  germ-cells  is  demonstrable 
very  early,  before  the  division  of  labour  implied  in  building 
up  the  body  has  more  than  begun.  Even  when  this  early 


THE  CYCLE  OF  LIFE 


379 


FIG.  59. — Chain  of  embryos  (E,)  of  Encyrtus  fuscicollis,  all  arising  from 
one  ovum,  bound  together  by  a  chain  of  mucus  (s.  )  After  Marchal. 


segregation  of  the  germ-cells  is  not  demonstrable,  we  know 
that  the  germ-cells  do  not  arise  from  differentiated 
body-cells.  They  are  cells  which  retain  intact  the 
qualities  of  the  fertilized  ovum  which  gave  rise  to  the 
parent.  Similar  material  to  start  with,  similar  conditions 
in  which  to  develop — therefore,  like  tends  to  beget  like. 
Two  famous  quotations  may  make  this  fundamental  fact 
of  germinal  continuity  quite  clear.  There  is  a  sense,  Galton 
said,  in  which  the  child  is  as  old  as  the  parent,  for  when 
the  parent's  body  is  developing  from  the  fertilized  ovum, 
a  residue  of  unaltered  germinal  material  is  kept  apart  to 
form  the  reproductive  cells,  one  of  which  may  become  the 
starting-point  of  a  child.  To  use  Weismann's  words  :  '  In 
development  a  part  of  the  germ-plasm  (i.e.,  the  essential 
germinal  material)  contained  in  the  parent  egg-cell  is  not 
used  up  in  the  construction  of  the  body  of  the  offspring, 
but  is  reserved  unchanged  for  the  formation  of  the  germ- 


38° 


THE   WONDER  OF  LIFE 


cells  of  the  following  generation '.  Thus  the  parent  is 
rather  the  trustee  of  the  germ-plasm  than  the  producer  of 
the  child.  In  a  new  sense,  the  child  is  a  '  chip  of  the  old 
block '. 

A  third  wonder  is  the  extraordinary  process  of  matur- 
ation or  '  reducing  division  '.  The  details  are  diverse  and 
difficult,  but  the  net  result  of  the  process  may  be  simply 


FIG.  60. — Part  of  a  dividing  cell,  a  Radiolarian,  showing  the  chromo- 
somes in  two  groups.  A,  the  cytoplasm  ;  c,  the  chromosomes  ; 
B,D,  differentiations  in  the  cytoplasm.  (After  Haecker.) 


stated.  In  each  cell  in  the  body  of  an  organism  there  is 
normally  a  nucleus  or  kernel,  and  within  the  nucleus  a 
definite  number  of  readily  stainable  rods,  or  loops,  or 
granules,  called  chromosomes.  Each  kind  of  living  creature 
has  a  particular  number,  thus  there  are  twenty- four  in  man, 
mouse,  and  lily ;  sixteen  in  ox,  guinea-pig,  and  onion ; 
twelve  in  the  grasshopper  ;  two  in  one  of  the  threadworms, 
and  so  on.  There  is  no  doubt  that  these  chromosomes  are 
very  important,  and  most  biologists  regard  them  as  the 


O 


THE  CYCLE   OF  LIFE  381 

bearers  or  vehicles  of  the  hereditary  qualities.  It  is  quite 
safe  to  say  that  the  chromosomes,  along  with  other  germ- 
cell  constituents,  stand  in  some  definite  causal  relation 
to  the  adult  characters.  Now  the  remarkable  fact  is  that, 
while  the  quite  immature  germ-cells  have  the  same  number 
(n)  of  chromosomes  as  the  body-cells  of  the  species  under 
consideration,  the  mature  germ-cells  have  half  that  number 

( -  ) .     By  a  kind  of  cell-division  (meiosis),  which  is  normally 

restricted  to  this  one  point  in  the  entire  life- history,  the 
number  of  chromosomes  is  reduced  to  one  half  the  normal 
number.  It  follows  that  when  the  ripe  spermatozoon 

and  the  ripe  ovum— each  with^  chromosomes— unite  in 

fertilization,  the  normal  number  n  is  restored.  If  there 
were  not  some  reduction  of  this  sort,  the  number  of  chromo- 
somes would  be  doubled  at  each  fertilization,  which  is 
absurd.  Moreover,  in  the  reduction,  which,  in  the  case 
of  the  egg,  means  the  absolute  rejection  of  half  of  the 
chromosomes  (which  are  usually  carried  off  by  the  first 
'  polar  body  '  and  come  to  nothing),  we  see  an  opportunity 
for  permutations  and  combinations  among  the  items  of 
the  inheritance,  e.g.  for  the  dropping  out  of  a  character 
altogether.  If  we  compare  the  inheritance  so  far  as  it 
is  borne  by  the  chromosomes  to  a  pack  of  cards,  there 
is  a  remarkable  throwing  away  of  half  of  the  pack  and 
their  replacement  by  half  of  another  pack  at  the  beginning 
of  each  individual  life. 

The  fourth  wonder  is  fertilization — the  intimate  and 
orderly  union  of  the  reduced  nuclei  of  the  two  sex- cells. 
There  are  several  processes  involved  which  may  be  analysed 
apart.  There  is  the  mingling  of  two  inheritances, 


382  THE  WONDER  OF  LIFE 

which  usually  come  from  two  different  parents,  and  it 
is  important  to  understand  that  the  spermatozoon  from 
the  one  parent  and  the  ovum  from  the  other  contribute 
the  same  number  of  chromosomes,  except  in  certain  very 
interesting  cases  where  half  the  spermatozoa  have  an  extra 
chromosome.  Furthermore,  anticipating  a  little,  we  may 
notice  the  ocular  demonstration  of  the  fact  that  when 
the  fertilized  ovum  divides,  each  daughter-cell  or  blastomere 
receives  the  normal  number  of  chromosomes,  half  of  which 
are  of  maternal  and  half  of  paternal  origin.  This  has  been 
followed  for  several  divisions,  so  that,  if  the  chromosomes 
are  (even  in  some  measure)  inheritance-bearers  we  have  a 
remarkable  confirmation  of  the  truth  of  the  prophetic 
statement  which  Huxley  made  in  1878  : 

'  It  is  conceivable,  and  indeed  probable,  that  every  part 
of  the  adult  contains  molecules  derived  both  from  the  male 
and  from  the  female  parent ;  and  that,  regarded  as  a  mass 
of  molecules,  the  entire  organism  may  be  compared  to  a 
web  of  which  the  warp  is  derived  from  the  female  and 
the  woof  from  the  male '. 

In  the  animal  kingdom  it  is  usual  for  cells  to  have  in  their 
cytoplasm,  outside  their  nucleus,  a  minute  body  known 
as  the  centrosome,  which  becomes  two  when  the  cell  is 
going  to  divide,  and  seems  to  play  an  important  part  in 
the  process  of  division.  In  the  animal  ovum  the  centrosome 
disappears,  and  it  is  part  of  the  process  of  fertilization  that 
the  spermatozoon  introduces  a  centrosome.  This  divides 
into  two,  and  these  have  their  role  when  the  egg  divides. 
One  passes  into  each  daughter-cell  or  blastomere. 

Another  aspect  of  fertilization  is  that  the  entrance  of  the 
spermatozoon,  or  the  reproductive  nucleus  of  the  pollen- 
grain  in  the  case  of  the  flowering  plant,  does  in  some  way 


THE   CYCLE   OF  LIFE  383 

stimulate  the  ovum  to  divide,  or  remove  some  embargo 
which  hinders  the  ovum  from  starting  on  its  course  of 
development.  It  is  possible  that  some  ferment  may  be 
introduced  in  ordinary  fertilization,  but  the  remarkable 
experimental  work  of  recent  years  shows  that  a  great 
variety  of  stimuli  may  serve  to  set  the  egg  dividing.  It 
is  difficult  to  discern  what  is  the  common  feature  in  these 
diverse  trigger-pulling  stimuli. 

Artificial  Parthenogenesis. — Our  knowledge  of  the 
very  interesting  phenomena  commonly  referred  to  as 
artificial  parthenogenesis  is  in  great  part  due  to  two 
experimenters  of  the  first  rank,  Professor  Jacques 
Loeb  and  Professor  Yves  Delage.  Loeb  began  by 
showing  that  the  action  of  the  male  element  could  be 
facilitated  or  its  range  of  possible  action  increased  by 
altering  the  conditions.  In  sea-water  rendered  faintly 
alkaline  the  eggs  of  the  sea-urchin  could  be  fertilized 
by  the  sperms  of  many  different  kinds  of  starfish,  though 
this  did  not  occur  in  ordinary  sea-water.  But  this  was 
but  the  beginning  of  his  remarkable  series  of  researches. 
He  put  the  eggs  of  the  sea-urchin  into  sea-water  to  which 
had  been  added  a  little  formic,  acetic,  or  butyric  acid, 
and  then  after  a  minute  or  two  replaced  them  in  normal 
sea-water.  They  began  to  show  the  initial  stages  of  nuclear 
division.  But  when  he  transferred  ova  from  the  acidified 
sea- water  to  more  concentrated  sea- water,  to  which  common 
salt  had  been  added,  they  developed  normally  and  at  the 
usual  rate,  and  formed  free-swimming  larvae.  Similar 
experiments  have  been  successfully  made  with  several 
kinds  of  worms  and  molluscs. 

Loeb,  Delage,  and  others  have  shown  in  a  considerable 
variety  of  cases  that  artificial  parthenogenesis  can  be 


384  THE  WONDER  OF  LIFE 

induced  by  many  different  kinds  of  stimulus.  To  set 
the  egg  dividing  a  mechanical  stimulus  such  as  gentle 
brushing  or  a  pin-prick  may  suffice  ;  or  a  slight  disturbance 
of  the  chemical  composition  of  the  sea- water  may  serve ; 
or  some  alteration  of  the  osmotic  conditions  by  adding 
something  to  the  water  ;  or  exposure  of  the  eggs  to  certain 
vapours  or  to  electric  discharges.  The  puzzling  feature 
is  the  diversity  of  effective  stimulus.  In  many  cases  the 
artificially  stimulated  egg  divides  and  re- divides,  but 
eventually  comes  to  naught.  In  a  few  cases,  viable  young 
animals  develop.  Thus  Professor  Delage  reared  a  miniature 
sea-urchin  from  an  unfertilized  ovum,  and  Fritz  Levy 
reared  young  frogs. 

Without  attempting  any  survey  of  the  very  striking 
series  of  experiments,  we  may  refer  to  two  or  three  which 
are  particularly  instructive.  Winkler  made  an  extract 
of  sea-urchin  spermatozoa  and  put  some  of  it  in  water 
containing  sea-urchin  eggs.  The  eggs  developed,  and  it 
was  inferred  that  the  extract  had  '  fertilized '  the  eggs. 
The  observation  was  right,  the  inference  was  wrong.  For 
Gies  and  Pichon  showed  that  Winkler's  results  were  due 
to  osmotic  influence.  The  same  results  can  be  obtained 
by  using  reagents  that  have  nothing  to  do  with  sperm- 
extract.  Kupelwieser  made  the  very  interesting  experi- 
ment of  bringing  the  spermatozoa  of  the  mussel  (Mytilus) 
into  contact  with  eggs  of  sea-urchins  (Strongylocentrotus 
and  Echinus),  with  the  result  that  the  eggs  developed  into 
larvae.  Microscopic  analysis  showed  that  the  chromo- 
somes of  the  mussel  spermatozoon  played  no  part  in  the 
fertilization,  but  that  the  centrosome  introduced  by  the 
spermatozoon  took  part  in  the  cleavage  process.  The 
larvae  showed  only  maternal  characters. 


THE  CYCLE  OF  LIFE  385 

Very  striking  experiments  have  been  made  by  M.  Bataillon 
on  frogs'  eggs,  and  confirmed  by  M.  Henneguy.  Under 
proper  precautions  the  eggs  were  taken  from  a  frog,  placed 
in  a  flat  dish,  pricked  with  a  needle  of  platinum  or  glass, 
and  then  covered  with  a  layer  of  water  which  had  been 
sterilized  by  heat.  In  about  four  hours  the  eggs  began  to 
segment,  and  about  a  fifth  of  them  did  it  normally.  Out 
of  a  thousand  eggs,  a  hundred  and  twenty  hatched  into 
tadpoles,  and  one  of  these  lived  till  it  was  about  three  months 
old  and  almost  a  perfect  frog.  As  it  has  been  remarked, 
'  in  the  hands  of  these  physiologists,  the  little  needle  was  as 
potent  (or  almost  as  potent)  as  Aaron's  rod '. 

In  one  of  his  experiments,  Bataillon  took  a  piece  of  a 
string  of  toad's  spawn  with  as  little  jelly  as  possible,  put  it 
in  a  dry  dish,  bathed  it  with  a  little  blood,  and  made  little 
punctures  in  the  eggs.  They  segmented  '  magnificently  ', 
and  the  frog's  blood  works  as  well  as  the  toad's,  and  better 
than  the  spermatozoa  of  the  frog  !  According  to  Bataillon, 
pricking  the  eggs,  or  exposing  them  to  vapour  of  chloroform, 
or  subjecting  them  to  electric  discharges,  and  the  like, 
may  be  sufficient  to  activate  the  eggs  and  induce  some 
cleavage.  But  if  embryos  and  larvae  are  to  be  developed, 
there  must  be  something  more ;  there  must  be  an  intro- 
duction of  some  organic,  apparently  nuclear,  matter,  which 
probably  exerts  a  catalytic  influence.  Thus  frogs'  eggs 
moistened  with  blood  and  then  pricked  will  develop  into 
larvae.  The  pin-prick  plus  the  introduced  blood  corpuscle 
take  the  place  of  the  spermatozoon  in  normal  fertiliza- 
tion. 

Fritz  Levy  followed  the  method  of  pricking  the  frogs' 
eggs  with  a  platinum  needle,  which  was  sometimes  first 
dipped  in  salt  or  in  the  blood  of  the  mother.  He  repeatedly 

c  c 


386  THE  WONDER  OF  LIFE 

reared  tadpoles  by  this  aspermic  development,  and  he  was 
thrice  successful  in  reaching  the  stage  of  miniature  frogs. 
It  is  interesting  to  find  that  the  nuclei  were  smaller  than 
the  normal,  and  Levy  believes  that  they  had  only  half  the 
normal  number  of  chromosomes. 

The  experiments  in  question  illustrate  very  clearly  that, 
as  we  have  indicated,  several  quite  distinct  things  take 
place  in  ordinary  fertilization.  The  entrance  of  the  sper- 
matozoon implies  some  degree  of  mingling  of  the  paternal 
with  the  maternal  inheritance,  and  it  also  implies  some 
stimulus  to  cleavage  or  the  removal  of  some  hindrance. 
In  the  artificial  parthenogenesis  effected  by  MM .  Bataillon 
and  Henneguy  the  role  of  sperm- stimulus  was  discharged 
by  a  needle,  and  the  inheritance  remained,  of  course,  purely 
maternal,  for  there  cannot  be  a  hybrid  between  a  needle 
and  a  frog.  As  a  French  writer  puts  it :  '  il  ne  peut  etre 
question  d'heredite  du  cote  du  pere,  car  on  ne  voit  pas 
tres  bien  les  jeunes  grenouilles  heritant  des  proprietes  de 
leur  epingle  paternelle '.  While  some  incline  to  think 
that  the  spermatozoon  introduces  a  stimulus,  perhaps  of 
the  nature  of  a  ferment,  Loeb  has  suggested  that 
the  spermatozoon  may  remove  '  a  negative  catalyser  or 
condition ',  the  presence  of  which  somehow  keeps  the 
ovum  from  developing.  The  stimulus  may  be  the  removal 
of  an  inhibitory  influence.  Further  experiments  are  re- 
quired before  this  question  can  be  securely  answered. 

We  have  seen  that  a  quite  ripe  ovum  has  in  its  nucleus 
half  the  normal  number  of  chromosomes  ;  if  this  ovum  be 
artificially  stimulated  to  development,  the  cells  of  the 
young  animal  should  also  contain  only  half  the  normal 
number.  According  to  Dehorne,  this  was  the  case 
in  an  eight  days'  old  frog-tadpole,  reared  from  an 


THE   CYCLE   OF  LIFE 


387 


unfertilized  egg ;  the  cells  of  the  body  had  only  half 
the  normal  number  of  chromosomes.  In  some  cases 
the  number  seems  to  be  normal,  which  may  be  due 
to  the  fact  that  the  ova  began  to  develop  under  arti- 
ficial stimulus  before  the  ordinary  reduction  process 
had  occurred;  or  to  a  subsequent  restoration  of  the 
reduced  number  '  by  a  process  of  auto-regulation ',  as 
is  said  to  be  the  case  in  Delage's  parthenogenetic  sea- 
urchin  larvae. 

The  general  opinion  of  experts  is  thus  summed  up  by 
Professor  E.  B.  Wilson.  As 
the  ovum  is  much  the 
larger,  it  is  believed  to 
furnish  the  initial  capital 
— including  in  some  cases 
a  legacy  of  food-yolk — for 
the  early  development  of 
the  embryo.  From  both 
parents  alike  comes  the 
inheritedorganizationwhich 
has  its  seat  (in  part  at  least) 
in  the  readily  stainable 
chromatin  rods  or  chromo- 
somes of  the  nucleus.  From 

the  father  comes  a  little  body,  the  centrosome,  which 
organizes  the  machinery  of  division  by  which  the  egg 
splits  up,  and  distributes  the  dual  inheritance  equally 
between  the  daughter-cells.  Besides  bearing  the  paternal 
inheritance,  restoring  the  number  of  chromosomes  to 
the  normal,  introducing  the  centrosome  (which  serves  as 
'the  weaver  of  the  loom'),  and  acting  as  the  normal 
trigger- puller  which  sets  the  egg  a-going  on  the  path- 


or  readily  stainable  bodies  in 
the  nucleus  ;  3,  the  cell  sub- 
stance or  cytoplasm  showing 
a  reticular  structure  ;  4,  the 
cell-wall. 


388  THE   WONDER  OF  LIFE 

way  of  development,  the  spermatozoon  may  do  yet 
another  thing.  In  some  insects  and  other  types,  half  of 
the  spermatozoa  have  the  same  number  of  chromosomes  as 

the  ripe  egg  ( - ),  while  half  of  them  have  one  fewerf  — 1 ), 
\2'  \2       ' 

and  there  seems  to  be  good  evidence  that  when  two  equal 
numbers  come  together  f--j — J  the  result  is  a  female, 

while    an  ovum  fertilized  by  a  spermatozoon  with  -  — 1 

2 

chromosomes  develops  into  a  male. 

We  see,  then,  how  much  is  involved  when  a  spermatozoon 
fertilizes  an  ovum.  There  is  a  mingling  of  the  paternal 
and  maternal  inheritances ;  there  is  a  restoration  of  the 
normal  number  of  chromosomes  ;  there  is  the  introduction 
of  the  minute  centrosome  which  plays  an  important  role  in 
cleavage  ;  there  is  an  activation  of  the  egg  and  a  stimulus 
to  embryo-forming ;  and  there  is  a  rapid  change  effected 
in  the  periphery  of  the  ovum,  so  that  it  becomes  non- 
receptive  to  other  spermatozoa. 

A  glimpse  into  the  subtleties  that  lie  beyond  may  per- 
haps be  given  by  taking  a  particular  item  of  fact.  Giinther 
Hertwig  finds  that  the  eggs  of  the  Edible  Frog  (Rana 
esculenta)  and  the  Common  Toad  (Bufo  vulgaris)  may  be 
fertilized  by  sperms  of  the  Brown  Frog  (Rana  fusca).  They 
segment  normally,  but  they  die  before  they  reach  the 
gastrula  stage  of  development.  But  if  the  spermatozoa 
of  Rana  fusca  be  first  exposed  to  intense  Radium  rays, 
and  then  used  for  fertilization,  the  eggs  develop  into  larvae 
which  survive  for  several  weeks.  The  explanation  sug- 
gested of  this  curious  paradox  may  be  wrong,  but  it  is 
illustrative.  It  is  this,  that  the  spermatozoa  of  R.  fusca 


THE  CYCLE   OF  LIFE  389 

contain  some  nuclear  element  which  is  not  in  harmony 
with  the  particular  protoplasmic  composition  of  the  eggs 
of  the  Edible  Frog  and  the  Common  Toad.  But  if  this 
disharmonious  element  be  destroyed  by  the  Radium  in- 
fluence, the  spermatozoon  may  act  as  a  stimulus  to  develop- 
ment— which  is,  in  a  sense,  parthenogenetic.  In  various 
organs,  it  was  noted  that  the  surface  or  volume  of  the 
nuclei  was  half  the  normal. 

Another  side-light  may  be  illuminating.  In  many  cases 
it  is  possible  to  effect  artificial  hybridisation,  even  between 
types  which  are  very  far  apart.  A  very  striking  instance 
is  that  effected  by  Professor  E.  W.  MacBride  between  the 
eggs  of  the  common  heart-urchin  (Echinocardium  cordatum) 
and  the  sperms  of  the  common  regular  sea-urchin  (Echinus 
esculentus).  The  hybrid  larvse,  which  showed  both  pater- 
nal and  maternal  characters,  lived  for  only  eight  or  nine 
days,  but  all  Echinoderm  larvse  are  delicate  and  difficult 
to  rear.  The  interest  of  the  case  is  that  the  two  parent 
genera  are  so  far  apart.  Professor  MacBride  points  out  that 
Echinus  and  Echinocardium  have  been  distinct  since  the 
beginning  of  the  Secondary  epoch,  and  that  their  common 
ancestor  could  not  have  lived  later  than  a  period  which  a 
moderate  estimate  would  place  at  twenty  million  years  ago  ; 
yet  the  germ-cells  of  the  two  types  will  commingle  so  as 
to  produce  a  hybrid  in  which  both  paternal  and  maternal 
characters  are  represented. 

No  one  can  dream  of  dealing  in  a  facile  way  with 
development,  which  is  one  of  the  central  mysteries  of 
life,  but  we  wish  to  try  to  state  two  general  ideas. 
The  first  is  that  development  is  an  active  process  of 
self-expression.  This  may  be  illustrated  by  reference  to 
a  very  important  event  in  development,  namely,  the  out- 


3QO  THE  WONDER  OF  LIFE 

growth  of  nerve-fibres  and  the  establishment  of  specific 
nervous  connections  on  which  the  effectiveness  of  sub- 
sequent activity  depends.  In  1890  Kamon  y  Cajal  dis- 
covered at  the  end  of  the  embryonic  nerve  fibres,  at  a  very 
early  stage  in  their  development,  what  he  called  a  cone 
of  growth,  which  he  compared  to  the  finger-like  outgrowth 
or  pseudopodium  which  the  Amoeba  protrudes  when 
it  is  gliding  over  the  mud  of  the  pond. 
In  very  vivid  words  he  wrote  (1899)  : 

'  From  the  functional  point  of  view,  the  cone  of  growth 
may  be  regarded  as  a  sort  of  club  or  battering  ram, 
endowed  with  exquisite  chemical  sensitiveness,  with  rapid 
amoeboid  movements,  and  with  a  certain  impulsive  force, 
thanks  to  which  it  is  able  to  press  forward  and  overcome 
obstacles  met  in  its  way,  forcing  cellular  interstices  until 
it  arrives  at  its  destination '. 

This  was  in  great  part  a  prophetic  interpretation,  and 
many  have  vigorously  opposed  the  conclusion  that  the 
development  of  nerve  paths  is  really  due  to  the  protoplas- 
mic movement  on  the  part  of  the  nerve-cells.  But  brilliant 
confirmation  of  Kamon  y  CajaPs  view  has  been  recently 
afforded  by  Professor  Ross  Granville  Harrison,  to  whose 
work  we  wish  briefly  to  refer. 

Harrison's  experiments  show  that  two  elementary 
phenomena  are  involved  in  nerve  development  :  (a)  the 
formation  of  the  primitive  nerve  fibre  by  an  outflowing 
movement  of  the  protoplasm  of  a  nerve-cell,  and  (6)  the 
formation  of  neurofibrils  within  this  filament — a  process 
of  tissue  differentiation. 

'  It  is  through  the  former  that  the  specific  nerve  paths 
of  the  body  are  first  laid  down  '.  '  The  energy  of  outgrowth 


THE  CYCLE   OF  LIFE  391 

is  immanent  in  the  nerve-cell,  and  the  initial  direction  of 
outgrowth  is  already  determined  within  the  cell  before 
the  outgrowth  actually  begins.  The  formation  of  the 
fibre  is  therefore  an  act  of  self-differentiation  within  Roux's 
definition '. 

The  second  general  impression  that  we  get  from  the 
study  of  development  is  that  of  a  continuous  action  and 
reaction  between  an  implicit  organization  and  the  environ- 
ing conditions.  We  include  in  the  environing  conditions 
not  only  the  external  medium  and  its  energies,  and  the 
maternal  environment  where  such  exists,  but  also  the 
intra-embryonic  environment,  the  influence  of  surrounding 
cells  and  of  the  whole  on  any  particular  developing  unit 
or  area.  The  developing  organism  is  continually  trafficking 
with  its  environment,  and  the  result  is  a  function  of  the 
intrinsic  hereditary  nature,  on  the  one  hand,  and  of  the 
appropriate  environmental  nurture,  on  the  other. 

In  thinking  of  such  a  difficult  problem  as  embryonic 
development,  it  is  always  profitable  to  look  at  it  in  the 
light  of  the  development  of  which  we  are  most  immediately 
aware — the  development  of  our  own  mind  and  character. 
Of  a  truth  they  are  both  born  and  made.  Our  mind  is  in 
great  part  a  social  product ;  our  character  has  to  be  wrought 
out  in  conduct.  What  we  are  aware  of  is  '  the  expliciting 
of  the  implicit ',  the  actualizing  of  something  potential, 
action  and  reaction  between  our  hereditary  nature  and  a 
complex  environing  nurture.  Reading  back,  we  feel  sure 
that  the  same  general  idea  applies  to  embryonic  develop- 
ment. The  general  idea  is  that  of  the  seed  which  will 
not  germinate  except  in  suitable  soil,  and  duly  favoured 
with  sunshine  and  rain ;  but  we  wish  to  push  the  idea  back 
till  we  see  in  each  cell  of  the  embryo,  in  each  '  organ-forming 


392  THE  WONDER  OF  LIFE 

substance  '  or  plastosome,  a  seed  to  which  the  surrounding 
cells  supply  the  appropriate  environment  and  the  necessary 
liberating  stimuli.  Above  all,  we  must  not  think  of  the 
matter  too  simply,  too  mechanically.  That  mechanical 
factors  operate  directly  on  the  developing  embryo  will 
be  admitted  by  all.  There  are  bound  to  be  pressures  and 
tensions  and  the  like,  which  make  themselves  felt.  But  it 
has  to  be  borne  in  mind  that  the  essential  process  is  the 
active  expression  of  an  inconceivably  intricate  organiza- 
tion, which  has  been  gradually  wrought  out  through  tens 
of  thousands  of  years.  When  Professor  His  maintained  that 
the  large  eyes  of  the  young  chick  are  the  direct  cause,  by 
compression,  of  the  sharp  beak  of  the  bird,  he  was  taking 
too  simple  a  view  of  the  problem,  and  mistaking  the  cart 
for  the  horse. 

To  take  a  concrete  illustration  of  the  absolutely  essential 
influence  of  the  environment.  It  is  well  known  that  the 
absence  of  the  appropriate  temperature  at  a  critical  period 
may  have  a  profound  effect.  It  may  arrest  cell-divisions  in 
one  part  of  the  embryo  more  than  in  another,  and  strange 
aberrations  may  result.  Or  it  may  operate  by  hindering 
the  operation  of  certain  ferments.  Thus  Dr.  J.  Dewitz 
placed  the  nests  of  a  wasp  (Polistes)  in  a  refrigerator  for 
forty-eight  hours,  and  found  that  this  had  the  effect  of 
hindering  the  development  of  the  wings  in  the  pupae. 
Similar  experiments  with  the  pupae  of  the  blow-fly  (Calli- 
phdra)  also  resulted  in  defective  wings.  Again  we  are  made 
to  feel  that  each  stage  in  development  has  its  appropriate 
external  nurture. 

Environment  affords  or  denies  stimulus,  and  according 
to  the  liberality  or  parsimony  will  be,  in  many  cases,  the 
degree  of  development  attained  by  the  animal.  A  diagram- 


THE  CYCLE   OF  LIFE  393 

matic  illustration  may  be  found  in  the  story  of  Neptune's 
Cup.  This  huge  cup-like  sponge  (Poterion  neptuni  or 
Cliona  patera)  may  grow  to  an  immense  size — a  cup  that 
only  a  god  could  drain.  It  may  be  a  couple  of  feet  in 
height.  Now  Vosmaer  discovered  what  Topsent  has  con- 
firmed, that  this  huge  cup  is  the  free  form  of  a  small  boring 
sponge  which  is  found  making  gimlet-like  holes  in  shells. 
There  are  also  free  and  prisoner  forms  of  the  common 
Cliona  celata. 

Growth. — The  power  of  growth  is  one  of  the  insignia  of 
life.  It  is  characteristic  of  all  living  creatures,  and  every  one 
knows  in  a  practical  way  what  it  means,  though  a  precise 
definition  is  not  easy.  One  may  say  that  growth  is  increase 
in  the  size  or  volume  of  an  organism,  and  usually  implies 
increase  in  mass  or  weight.  But  there  is  evidently  no 
small  difference  between  an  increase  of  size  due  to  a  sub- 
cutaneous deposit  of  fat,  such  as  we  see  in  prize  pigs  and 
prize  fat  cattle,  and  the  slow  continuous  growth  of  a  lean 
fish  like  a  haddock.  There  is  a  marked  difference  between 
an  enlargement  due  to  the  accumulation  of  watery  fluid 
and  the  fine  growth  of  an  embryo's  brain.  It  is  not  growth 
that  we  see  when  a  parched  turnip  or  the  like  is  surrounded 
with  water  and  expands,  or  when  a  frog,  leaving  its  winter- 
quarters  in  the  mud,  plunges  into  the  pond,  and,  absorbing 
water  through  its  skin,  may  be  watched  '  swelling  visibly  '. 
It  seems,  indeed,  that  more  than  one  word  is  required 
to  cover  the  various  phenomena  which  may  be  quite 
reasonably  referred  to  as  growth. 

We  cannot  speak  of  growth  as  one  of  the  characteristics 
of  living  organisms  without  remembering  that  the  power 
of  growth  under  suitable  conditions  is  also  the  fundamental 
property  of  crystals.  Since  Professor  Lehmarm  published 


394  THE  WONDER  OF  LIFE 

his  important  work  on  Fluid  Crystals  in  1904,  the  conception 
of  crystals  has  had  to  be  profoundly  altered.  For  he 
introduced  us  to  what  he  called  the '  new  world '  of  crystals 
that  are  mobile  and  liquid,  yet  not  separable  by  any  break 
from  those  that  are  rigid  and  solid.  The  fundamen- 
tal character  is  the  power  of  growing,  and  Professor 
Lehmann  thinks  that  this  may  be,  as  it  were,  utilized  in  the 
growth  of  organisms.  He  figures  the  beautiful  growths 
of  purely  inorganic  '  silicate- vegetation  '.  But  what  must 
be  definitely  borne  in  mind  is  that  the  crystal  can  only 
grow  larger  at  the  expense  of  material  the  same  as  itself. 

Organic  growth  is  essentially  a  regulated  increase  in 
the  amount  of  living  matter  (protoplasm)  and  intimately 
associated  substances.  It  is  much  more  than  accretion, 
it  is  an  active  process  of  self-increase.  Unlike  a  crystal's 
growth,  it  comes  about  at  the  expense  of  materials  different 
from  the  growing  substance — often  very  different,  as  in 
the  case  of  plants,  which  feed  on  air,  water,  and  salts. 
Unlike  mere  expansion,  it  is  regulated  in  relation  to  the 
organism,  or  organ,  or  cell  that  is  growing.  In  all  multi- 
cellular  organisms  growth  is  associated  with  cell-division, 
for  when  the  individual  cell  reaches  its  limit  of  growth  it 
divides  into  two. 

As  to  the  conditions  of  growth,  the  first  is  Nutrition. 
Living  involves  continual  wear  and  tear  and  not  less 
continual  recuperation ;  growth  depends  on  there  being 
a  surplus  in  the  process  of  self -renewal.  In  other  words, 
it  is  a  fundamental  condition  of  growth  that  income 
should  be  greater  than  outlay.  Thus  the  enormous  bulk 
of  many  plants — like  the  Big  Trees  of  California — is  in  part 
dependent  on  the  fundamental  fact  that  the  income  of  the 
plant  is  always  high  above  its  expenditure.  Animal  giants 


THE  CYCLE  OF  LIFE  395 

are  rare,  and  one  of  the  reasons  for  this  is  that  animals  live 
much  more  nearly  up  to  their  income  than  plants  do. 
It  sometimes  happens,  one  must  admit,  that  an  organism 
grows  larger  for  a  time  without  taking  in  any  food — we  can 
see  that  in  the  growth  of  salmon-fry  before  they  begin  to 
eat — but  what  happens  in  such  cases  is  a  change  of  con- 
densed stored  substances  into  more  dilute  and  bulkier  form. 
The  embryo  is  cashing  and  re-investing  its  legacy  of  yolk. 
The  same  is  true  of  the  shoots  of  a  potato,  sprouting  in  a 
dark  cellar ;  they  show  true  growth  though  the  organism 
as  a  whole  is  actually  losing  water  in  transpiration,  and, 
as  its  respiration  shows,  breaking  down  carbon-compounds. 
What  was  stored  in  the  tuber  is  being  transformed. 

More  difficult,  perhaps,  is  the  case  of  a  young  tadpole, 
for  careful  measurements  and  weighings  show  that  during 
the  period  of  most  rapid  growth,  the  weight  of  dry  sub- 
stance does  not  increase  at  all.  During  this  period,  it 
seems,  the  imbibition  of  water  is  more  important  than  the 
assimilation  of  food-material. 

Plenty  of  assimilated  food  is  the  sine  qua  non  of  growth, 
but  the  conditions  imply  appropriate  environment  along 
other  lines.  Growth,  like  development,  has  its  optimum 
environment,  but  this  differs  so  much  for  different  organisms, 
that  it  is  difficult  to  make  general  statements  in  regard 
to  the  agencies  that  favour  and  those  that  hinder  growing. 
What  is  one  organism's  meat  is  another  organism's  poison. 
In  a  general  way,  it  might  be  said,  light  is  essential  for  the 
growth  of  plants,  for  the  assimilatory  process  of  building 
up  carbon  compounds  is  a  photo-synthesis  dependent  on 
the  sunlight.  But  when  we  look  into  the  matter  more 
carefully  we  find  that,  other  things  being  equal,  plants 
grow  more  rapidly  during  the  night  than  during  the  day. 


396  THE  WONDER  OF  LIFE 

The  strongly  refractive,  so-called  chemical  rays,  which 
have  little  or  no  effect  on  assimilation,  have  an  inhibiting 
effect  on  growth.  The  growth  of  plants  is  also  dependent 
on  humidity,  the  amount  of  oxygen,  temperature,  electrical 
conditions,  and  other  influences.  The  optimum  tempera- 
ture usually  lies  between  22°  and  37°  C.,  and  there  is  a 
complete  cessation  of  growth  in  plants  at  a  temperature 
less  than  0°  C.  or  higher  than  40°-50°  C. 

For  animals  the  general  statement  may  be  made  that 
lowering  the  temperature  puts  a  brake  on  growth.  It  does 
so,  in  part,  by  retarding  the  process  of  cell-division,  and 
it  does  this,  in  part,  by  retarding  the  up-building  of  nuclein 
compounds  in  the  cells.  Growth  is  much  slower  in  polar 
than  in  tropical  seas,  and  the  life-span  is  more  drawn  out. 
For  a  developing  chick,  the  temperature  above  which  death 
occurs  is  43°  C.,  the  minimum  at  which  growth  stops  is 
about  28°  C.,  the  normal  limits  are  between  35°  and  39°  C. 

Some  light  on  the  difficult  question  of  the  limit  of  growth 
may  be  obtained  from  a  simple  consideration  in  regard 
to  cell-growth,  which  seems  to  have  been  made  independ- 
ently by  Herbert  Spencer,  Kudolf  Leuckart,  and  Alex- 
ander James.  Cells  may  be  defined  as  unit  areas  or  cor- 
puscles of  living  matter,  and,  as  we  have  already  noted, 
the  growth  of  multicellular  organisms  depends  on  the 
growth  and  division  of  the  component  cells.  A  cell  may 
grow  by  taking  up  water,  and  by  accumulation  of  the  by- 
products of  metabolism,  but  essentially  by  having  a  surplus 
in  the  continual  recuperation  of  the  living  matter.  Now, 
if  we  start  with  a  spherical  cell  and  suppose  it  to  grow 
until  it  has  quadrupled  its  original  volume,  it  has  by  no 
means  quadrupled  its  surface,  for  the  volume  increases 
as  the  cube  of  the  radius,  and  the  surface  only  as  the  square. 


THE   CYCLE  OF  LIFE  397 

But  as  it  is  through  its  surface  that  the  cell  is  fed,  aerated, 
and  purified,  functional  difficulties  are  bound  to  set  in  as 
the  increase  of  surface  lags  behind  the  increase  of  volume. 
There  is  four  times  as  much  material  to  be  kept  alive,  but 
there  is  not  four  times  the  surface  by  which  to  effect  this. 
A  free-living  cell,  like  an  Amoeba,  evades  the  functional 
dilemma  by  flowing  out  into  irregular  processes,  which 
greatly  increase  the  surface,  making  the  cell  like  a  country 
with  a  much-indented  coast-line.  But  what  ordinarily 
happens  is  that  when  the  cell  has  reached  its  limit  of  growth, 
the  maximum  safe  size,  it  divides  into  two,  halving  its 
volume  and  gaining  new  surface.  As  a  general  rationale, 
applicable  mutatis  mutandis  to  organs  and  organisms  as 
well  as  to  cells,  the  suggestion  thus  briefly  outlined  certainly 
helps  towards  an  understanding  of  the  limit  of  growth. 
Another  important  suggestion  has  been  advanced  by 
Boveri  and  Richard  Hertwig,  that  the  limit  of  growth  is 
in  part  determined  by  the  ratio  of  the  amount  of  nuclear 
material  to  the  amount  of  cell- substance  or  cytoplasm. 
When  an  animal  grows  larger  this  usually  means  that 
its  cells  are  multiplying,  but  it  has  been  suggested  (by 
Plenk)  that  in  lower  animals  of  small  size,  such  as  Rotifers 
and  some  Nematodes,  an  increase  in  the  dimensions  of  the 
cells  plays  an  important  part  in  growth.  In  the  cells  of 
some  animals  with  small  eggs,  such  as  lampreys  and  sala- 
manders, there  is  some  increase  in  the  size  of  the  elements, 
and  the  same  is  true  of  very  large  cells  in  higher  animals, 
and  of  permanent  elements  like  ganglion-cells,  muscle-cells, 
and  lens-fibres,  which  lose  their  power  of  division  at  a  very 
early  stage.  On  the  whole,  however,  cell-multiplication 
is  the  main  factor  in  growth.  The  most  characteristic 
feature  of  a  growing  organism  is  that  it  is  normally  self- 


398  THE  WONDER   OF  LIFE 

regulated.  In  the  beautiful  growth  of  a  crystal  in  the 
midst  of  its  solution,  there  is  some  degree  of  regulation 
in  relation  to  the  already  existing  architecture.  Although 
we  may  not  understand  much  about  it,  we  see  that  the 
growth  of  the  crystal  is  not  higgledy-piggledy  addition, 
but  an  orderly  and  proportioned  crystallization.  But  this 
is  far  more  deeply  true  of  organic  growth,  which  implies  a 
regulated  series  of  phenomena,  occurring  in  a  certain 
sequence  and  within  certain  limits.  If  the  sequence  be 
disturbed  or  the  limits  be  crossed,  then  there  is  something 
abnormal.  The  regulation  is  comparable  to  that  which 
we  see  in  the  erection  of  a  properly-designed  building — 
there  is  a  style  and  a  plan  to  be  adhered  to,  there  are  laws 
of  proportion  to  be  respected,  there  is  even  a  normal  rate 
which  must  not  be  disregarded.  In  the  same  way,  the 
regulation  of  organic  growth  has  reference  to  the  specific 
constitution  of  the  organism  (its  structural  organization 
on  the  one  hand  and  its  characteristic  metabolism  on  the 
other),  and  that  means  that  it  has  reference  to  the  past 
history  or  evolution  of  the  organism.  This  subtle  quality 
of  regulatedness  is  one  of  the  criteria  of  organic  growth, 
and  it  seems  to  many  biologists  to  remove  it  far  from  the 
mere  multiplication  of  chemical  substances,  or  from  the 
continued  action  of  a  ferment  as  long  as  material  to  ferment 
is  supplied. 

One  of  the  ways  in  which  the  regulation  of  growth  is 
brought  about  within  the  organism  is  by  means  of  inter- 
nal secretions  or  '  hormones '.  These  are  produced  by 
glands  or  glandular  tissues  in  various  parts  of  the  body, 
and  are  passed  into  the  blood.  They  are  transported  hither 
and  thither  and,  when  they  come  into  close  quarters  with 
susceptible  parts,  they  stimulate  or  hinder  growth.  Thus 


THE   CYCLE   OF  LIFE  399 

it  is  well  known  that  the  internal  secretions  of  the  thyroid 
gland  which  lies  on  each  side  of  the  larynx  (or  '  Adam's 
apple'),  and  of  the  pituitary  body  (a  remarkable  organ 
which  is  appended  to  the  floor  of  the  brain)  have  a  specific 
regulatory  effect  on  the  growth  of  the  brain,  the  subcu- 
taneous tissue,  and  the  bones.  It  is  said  that  a  youth  who 
had  been  a  successful  candidate  for  a  military  post,  but  was 
debarred  because  of  inadequate  height,  was  able  by  a 
judicious  use  of  pituitary  extract  (obtained  from  ox  and 
sheep)  to  add  in  a  few  months  the  peremptorily  required 
cubit  to  his  stature.  It  has  been  shown  that  the  internal 
secretions  of  the  reproductive  organs  in  vertebrate  animals 
have  a  specific  effect  on  the  growth  of  various  parts  of  the 
body,  both  of  important  organs,  like  the  milk-glands  in 
mammals,  and  trivial  decorative  structures,  like  the  comb 
in  poultry.  It  seems  certain  that  some,  if  not  all,  human 
giants  are  the  result  of  the  exaggerated  secretion  of  the 
pituitary  body,  and  it  is  possible  that  some  kinds  of  dwarfs 
are  due  to  a  deficiency  of  the  same  stimulus. 

Even  when  we  cannot  at  present  suggest  a  physiological 
interpretation,  such  as  the  influence  of  a  specific  secretion, 
the  fact  of  the  regulation  of  growth  must  be  recognized. 
Different  parts  grow  at  very  different  rates,  yet  the  normal 
result  is  proportionate  growth.  In  cases  of  under-feeding, 
there  is  great  diversity  in  the  effect  on  different  organs  ; 
they  do  not  suffer  alike.  This  points  to  a  remarkable 
internal  regulation  of  growth.  More  familiar,  and  perhaps 
simpler  illustrations  of  the  internal  correlation  may  be 
found  in  cases  where  an  organ,  such  as  the  heart,  responds 
by  increased  growth  to  increased  demands  upon  it. 

Galls  are  often  formed  by  plants  in  response  to  some 
external  stimulus,  such  as  the  salivary  secretion  of  the  larval 


400  THE  WONDER   OF  LIFE 

gall-insect  which  has  emerged  from  its  egg-envelope  de- 
posited within  the  tissue  of  the  leaf  or  stem.  In  these  cases 
we  have  very  striking  instances  of  specific  secretions  induc- 
ing specific  kinds  of  growth.  These  are  extraneous 
secretions  introduced  into  the  plant  by  an  animal,  but 
we  have  also  evidence  of  intrinsic  secretions  within  the 
plant  which  help  to  regulate  growth.  Thus  it  is  said  that 
in  the  growth  of  the  roots  of  some  plants,  specific  chemical 
substances  are  formed  which  inhibit  further  growth.  In 
short,  facts  are  accumulating  which  show  that  particular 
parts  of  an  organism  have  their  growth  regulated  by  specific 
internal  secretions. 

In  his  Principles  of  Biology  Herbert  Spencer  devoted 
much  attention  to  the  conditions  of  growth.  He  sought 
to  show  that  growth  varies — other  things  equal — (1 )  directly 
as  nutrition,  (2)  directly  as  the  surplus  of  nutritive  income 
over  expenditure,  (3)  directly  as  the  rate  at  which  this 
surplus  increases  or  decreases,  (4)  directly  (in  organisms 
of  large  expenditure)  as  the  initial  bulk,  and  (5)  directly 
as  the  degree  of  organization.  This  kind  of  analysis  is 
valuable,  but  what  is  more  needed  at  present  is  an 
extensive  series  of  measurements  of  growth  under  diverse 
conditions  and  in  different  kinds  of  organisms. 

It  is  interesting  to  inquire  into  the  periods  and  rates 
of  growth  in  different  organisms.  After  an  egg-cell  has 
been  fertilized  it  divides  and  re-divides,  but  for  a  time, 
though  there  is  increase  in  the  number  of  cells,  there  is 
no  increase  in  size.  We  see  development,  but  no  growth. 
Soon,  however,  development  and  growth  proceed  hand  in 
hand,  both  very  rapidly.  Later  on,  when  development  is 
proceeding  slowly — all  the  chief  steps  having  been  taken — 
growth  may  still  continue  very  vigorously,  Thus  in  the 


THE   CYCLE  OF  LIFE  401 

pre-natal  life  of  man,  great  strides  in  development  are 
taken  in  the  first  three  months,  along  with  very  rapid 
growth.  Thereafter,  when  the  developmental  steps  are 
much  less  striking,  the  growth  is  for  a  time  very  rapid. 
From  the  third  to  the  fourth  ante-natal  month,  the  increase 
is  600  per  cent.  After  this  it  drops  quickly  and  is  barely 
25  per  cent,  in  the  last  month  before  birth. 

In  some  organisms  the  growing  period  is  very  sharply 
punctuated ;  thus  in  insects  with  complete  metamorphosis 
all  the  growing  is  done  in  the  larval  period.  After 
the  fully-formed  winged  insect  emerges  from  the  pupa- 
stage,  there  is  no  increase  in  size.  This  holds  good  in  all 
butterflies  and  moths ;  ants,  bees,  and  wasps ;  beetles; 
and  two-winged  flies.  In  many  cases  the  adult  does  not 
feed  at  all,  and  there  is  the  sharpest  contrast  between 
the  larva  which  feeds,  grows,  stores,  and  moults, 
and  the  adult  or  imago  which  does  not  grow  or  moult, 
but  is  especially  concerned  with  the  continuance  of  the  race. 

In  other  cases  growth  appears  to  have  no  limit  but 
the  length  of  the  life-tether.  As  long  as  the  organism  lives 
and  feeds  it  may  go  on  growing.  Thus  we  may  distinguish 
the  indefinite  or  indeterminate  growth  of  fishes  and  reptiles 
from  the  definite  or  determinate  growth  of  birds  and 
mammals.  A  sacred  crocodile  may  continue  slowly  growing 
year  after  year,  and,  it  is  said,  decade  after  decade.  It  is 
not  uncommon  to  get  huge  haddocks  as  large  as  good-sized 
cod-fish,  but  there  is  very  little  variation  in  the  size  of  a 
sparrow  or  of  a  squirrel.  In  other  words,  some  organisms 
show  a  very  definite  limit  of  growth — the  physiological 
optimum — while  others  do  not. 

An  interesting  feature  about  growth  is  the  occurrence 
of  minor  periodicities.  Partly  no  doubt  because  of  its 

DD 


402  THE  WONDER   OF  LIFE 

dependence  on  nutrition  and  on  external  agencies,  growth 
is  often  punctuated  in  some  detail.  Every  one  is  familiar 
with  the  annual  rings  of  growth  seen  on  the  cross-section 
of  a  tree — seen  so  clearly  because  there  is  an  alternation 
of  summer  wood  and  autumn  wood  differing  in  texture. 
The  more  prominent  lines  on  the  shell  of  the  freshwater 
mussel  indicate  years  and  the  weaker  lines  between  these 
indicate  minor  periodicities.  But  the  finest  registering 
is  seen  on  the  scales,  in  the  ear-stones,  and  even  in  some 
of  the  bones  of  many  fishes. 

Besides  the  periodicities  of  growth  which  can  be  reason- 
ably correlated  with  external  periodicities,  such  as  those  of 
the  seasons,  there  are  others  of  a  more  recondite  nature, 
such  as  phases  of  quick  growth  and  slow  growth,  that  alter- 
nate in  the  development  of  some  animals,  as  Fischel  has 
shown,  for  instance,  in  the  development  of  the  duck.  It  is 
probable  that  these  differences  of  rate  are  connected  with 
the  periodic  liberation  of  internal  secretions  within  the 
growing  organism. 

The  rate  of  growth  has  been  carefully  studied  in  a  few 
cases,  e.g.  in  guinea-pigs  by  Minot,  and  the  facts  are 
striking.  In  guinea-pigs  there  is  in  both  sexes  a  decline 
in  the  growth-rate  almost  from  the  moment  of  birth.  The 
decline  of  rate  is  rapid  from  about  the  fifth  day  to  about 
the  fiftieth ;  from  the  fiftieth  day  onwards  the  decline 
is  slower,  until  the  growth  stops  altogether.  Of  course  the 
animal  is  growing  a  great  deal,  and  very  quickly  too,  in  its 
early  days,  but  the  rate  of  growth  gets  less  and  less.  More- 
over, the  post-natal  decline  in  the  growth-rate  appears  to 
be  a  continuation  of  an  ante-natal  decline.  As  Dr.  Jenkin- 
son  puts  it,  '  The  younger  the  animal,  the  faster  it  grows  ; 
the  more  developed  it  is,  the  more  slowly  it  grows.  The 


THE   CYCLE   OF  LIFE  403 

rate  of  growth,  in  fact,  varies  inversely  with  the  degree  of 
differentiation '. 

In  Man  there  are  three  maxima  of  rate  of  growth.  The 
first  is  before  birth,  but  its  precise  occurrence  is  uncertain. 
As  we  have  already  mentioned,  the  increment  from  the 
third  to  the  fourth  month  is  600  per  cent.  It  then  falls 
with  great  rapidity  between  the  fourth  and  sixth  months, 
and  thereafter  more  slowly  till  birth.  The  second  maxi- 
mum is  in  the  first  year  of  infancy,  when  the  increase  of 
weight  is  (according  to  Minot)  about  200  per  cent.,  and 
the  length  (according  to  Schwerz)  increases  from  50  centi- 
metres to  about  75  centimetres.  In  the  following  five 
or  six  years  the  rate  of  growth  becomes  slower  and  slower. 
The  third  maximum  is  towards  the  time  of  puberty,  at 
about  the  age  of  twelve  to  thirteen  for  girls,  of  fourteen  to 
sixteen  for  boys.  In  the  early  years  the  length  of  the 
body  increases  more  rapidly  than  the  weight ;  later  on, 
after  puberty,  increase  in  weight  takes  the  lead. 

An  interesting  point  in  regard  to  growth  is,  that  it 
may  differ  markedly  in  the  two  sexes.  The  male  is 
often  a  pigmy  compared  with  the  female,  though  the  egg- 
cells  from  which  they  developed  may  have  been  identical 
in  size.  The  growth  of  women  is  quite  different  from 
the  growth  of  men,  and  as  this  has  been  observed  in  all 
sorts  and  conditions,  in  many  countries  and  races,  it  cannot 
be  referred  to  differences  in  habits.  It  is  a  constitutional 
difference.  It  is  not  merely  that  the  growth  of  women  is 
7  per  cent,  less  than  that  of  men  ;  the  growth  is  on  a  different 
scheme,  with  the  parts  in  different  proportions. 

When  we  say  that  growth  is  a  regulated  increase  in  the 
amount  of  living  matter,  we  mean  that  it  is  not  a  steady 
continuous  increase  in  proportion  to  the  available  nutritive 


404  THE  WONDER   OF  LIFE 

income,  but  a  periodic  controlled  increase,  differing  in  its 
rate  in  different  species  and  at  different  times,  and  proceeding 
in  such  a  way  that  what  we  call  proportion  is  secured. 
Professor  Kellicott,  in  an  important  contribution  to  the 
theory  of  growth,  has  emphasized  the  same  idea  by  calling 
attention  to  the  diversity  in  the  rate  of  growth  of  different 
parts  of  the  body. 

In  the  smooth  dogfish  (Mustelus  canis)  the  various  organs, 
or  perhaps  tissues,  seem  to  grow  characteristically,  each 
having  an  individual  form  of  growth  curve.  The  rates 
of  growth  of  the  brain,  the  heart,  the  pancreas,  the  spleen, 
and  so  on,  are  different  from  the  rate  of  increase  in  total 
weight.  Indeed,  it  seems  to  Professor  Kellicott  that  in 
fishes,  which  are  organisms  of  indeterminate  growth,  the 
brain,  heart,  digestive  glands,  and  fins  do  not  always  keep 
pace  with  general  increase  of  trunk  musculature  and  connec- 
tive tissue,  and  a  loss  of  functional  equilibrium  results.  The 
fish  may  grow  too  large  for  its  heart  or  for  its  brain.  It 
cannot  be  doubted  that  the  determinate  growth  of  birds 
and  mammals  is  an  improvement  on  the  more  primitive 
unlimited  growth  of  fishes,  which  is  less  perfectly  regulated. 

When  we  consider  growth  in  its  entirety  as  a  regulated 
self -increase  of  the  whole  organism  and  of  its  parts,  we 
see  how  far  it  lies  beyond  the  present  limits  of  physico- 
chemical  interpretation.  The  analogous  phenomena  of 
chemical  polymerization  and  of  the  increase  of  crystals 
in  a  solution  are  certainly  interesting,  but  they  do  not 
seem  to  have  brought  us  more  than  a  little  way  nearer 
understanding  organic  growth.  That  an  organism  should 
keep  its  own  diary,  entering  therein  its  tradings  with 
time,  is  just  a  particular  case  of  what  is  either  a  wonder  or  a 
commonplace,  that  a  living  creature  is  characterized  by  this 


THE   CYCLE   OF  LIFE  405 

capacity  of  enregistering  within  itself  its  experiences.  In 
many  cases  we  do  not  know  enough  to  read  the  diary  ;  in 
many  cases  the  creature  destroys  its  own  records  in  the 
continuous  process  of  self-repair  or  of  replacement  of  old 
cells  by  new.  Here  we  feel  the  extraordinary  importance 
of  the  fact  that  in  higher  animals  there  is  no  replacement 
of  nerve-cells.  We  cannot  add  to  them  after  we  are  born. 

Young  Animals. — In  his  remarkable  book  on  The 
Childhood  of  Animals,  which  can  hardly  be  over-praised, 
Dr.  Chalmers  Mitchell  suggests  a  threefold  classification. 
There  are  young  animals  which  are  in  a  general  way  like 
miniature  editions  of  the  parents,  or  which,  at  any  rate, 
very  soon  become  like  their  parents,  as  is  the  case  with 
reptiles,  birds  and  mammals,  and  with  a  great  variety  of 
backboneless  animals,  such  as  cuttlefishes,  snails,  spiders, 
and  earwigs.  There  is  a  distinct  youthful  period,  with 
interesting  growth-changes,  but  young  and  old  are  of  the 
same  type. 

In  the  second  place,  there  are  animals  whose  young  stages 
are  very  unlike  the  parents,  with  a  different  kind  of  bodily 
structure — sometimes  on  a  quite  different  plan — and  with 
well-finished  adaptations  to  a  mode  of  life  very  different 
from  that  of  the  adults.  Tadpoles  are  very  different  from 
frogs,  and  caterpillars  from  butterflies.  The  young  of  the 
sedentary  water-bag-like  sea-squirts  are  free-swimming 
creatures  like  miniature  transparent  tadpoles,  and  no  one 
who  did  not  know  could  guess  that  the  '  Glass-crab  ' 
larva  would  become  a  rock-lobster.  These  larval  forms 
are  of  great  biological  interest,  and  their  marked 
unlikeness  to  their  parents  reaches  a  climax  in  most  of  the 
Echinoderms — (starfishes,  brittle-stars,  sea-urchins,  sea- 
cucumbers,  and  feather-stars),  where  the  free-swimming 


406  THE  WONDER  OF  LIFE 

pelagic  stage  is  utterly  different  from  the  adult  type. 
After  developing  for  a  while  on  a  line  of  its  own,  suited  to 
pelagic  life,  it  begins  again,  as  it  were,  on  a  new  tack,  and 
the  development  is  strikingly  circuitous  (Figs.  69,  70). 
Many  a  young  animal  received  a  name  of  its  own,  before 
zoologists  recognized  its  beginning  or  its  end.  Thus  the 
knife-blade-like  stage  in  the  life-history  of  eels  was  called 
Leptocephalus. 

The  third  group,  according  to  Chalmers  Mitchell,  includes 
those  animals  which  have  no  youth,  and  these  he  illustrates 
by  simple  creatures  like  Amosbse.  In  such  cases  the  unit 
which  starts  on  an  individual  life  of  its  own  is  already 
perfect ;  it  does  not  differ  in  protoplasmic  organization 
from  the  parent  cell  from  which  it  was  derived.  We  are 
inclined  to  think  that  it  would  be  equally  accurate  to 
say  that  these  simple  creatures  never  grow  up,  remaining 
eternally  young.  Ageing  began  when  a  body  began. 

When  we  think  over  our  experiences  of  young  animals, 
a  number  of  lasting  impressions  assert  themselves.  There 
is  the  extraordinary  abundance  of  life,  the  multitudes  of 
'  water-babies  ',  like  gnats  and  fish  fry  and  tadpoles,  and  of 
terrestrial  forms,  like  grubs  and  caterpillars  and  mice ; 
there  is  the  correlated  impression  of  the  abundance  of  death, 
out  of  a  million  oyster-embryos  but  one  survives ;  there 
is  the  plasticity  or  modifiability  of  young  things,  the 
experimental  tricks  that  can  be  played  with  tadpoles,  for 
instance,  being  notorious.  Another  impression  we  get  is, 
that  the  young  creature  does  often  in  some  measure  climb 
up  its  own  genealogical  tree,  for  there  is  a  great  truth  in  the 
seductive  and  much-abused  doctrine  of  recapitulation. 
Many  reservations  must  be  made,  e.g.  that  the  living 
creature  is  specific,  itself  and  nothing  else  from  first  to 


THE  CYCLE   OF  LIFE  407 

last ;  but  especially  in  the  making  of  organs  do  we  see  a 
succession  of  individual  stages  which  seem  to  correspond 
to  racial  steps.  The  doctrine  requires  careful  handling, 
but  we  think  that  the  facts  still  warrant  us  in  upholding  a 
cautious  statement  of  the  'Recapitulation  Doctrine  '- 
that  the  individual  development  of  an  organism  is  in  some 
respects  like  a  recapitulation,  often  much  condensed  and 
telescoped,  of  the  historical  evolution  of  the  race. 

In  our  Biology  of  the  Seasons  we  have  referred  to  another 
general  impression  which  arises  from  the  study  of  young 
animals — we  are  face  to  face  with  organic  inertia  on  the 
one  hand  and  organic  divergence  on  the  other.  On  the 
one  hand,  like  tends  to  beget  like  ;  '  the  child  is  as  old  as 
its  parents,  a  chip  of  the  old  block,  a  pendant  from  a  con- 
tinuous chain  of  germ-cells  '.  On  the  other  hand,  we  see 
'  the  tendency  to  vary,  to  be  something  new,  to  be  cre- 
ative. The  living  creature  is  a  Proteus.  In  a  deep  sense, 
the  little  child  leads  the  race '. 

The  old-fashionedness  of  young  animals  is  often  well 
illustrated  by  their  colour  and  markings.  They  tend  to 
show  the  primitive  kind  of  colouration  that  results  from 
general  physiological  conditions,  and  the  markings  that 
result  from  the  rhythms  of  growth.  This  colouration 
may  be  quite  useful  to  the  young  animals,  it  often 
seems  to  give  them  a  garment  of  invisibility ;  but  it  is 
primarily  a  result  of  constitution,  and  no  more  utilitarian 
than  ripple-marks  on  the  shore.  Chalmers  Mitchell  shows 
that  if  there  are  changes  in  subsequent  development  they 
are  usually  of  two  kinds — (1)  there  is  a  blurring  of  the 
original  pattern  and  a  toning  down  of  the  youthful  spotti- 
ness  and  emphasis,  for  in  the  adult  struggle  for  existence 
there  are  few  things  safer  than  the  monotony  of  '  self '- 


408  THE  WONDER  OF  LIFE 

colour ;  or  (2)  there  is  an  overlaying  of  the  old  colouring 
and  pattern  by  something  distinctively  new,  '  ruptive  ',  as 
he  calls  it.  The  new  types  of  colouration  are  increasingly 
utilitarian  and  are  proportionately  defined  by  Natural 
Selection.  We  say  '  new ',  but  what  occurs  is  probably 
an  analysis  of  the  '  old  ' ;  certain  factors  come  to  the  front 
and  others  recede.  Chalmers  Mitchell  uses  the  very 
instructive  analogy — perhaps,  as  he  hints,  much  more — 
of  the  dull  coal-tar  residues  from  which  have  been  analysed- 
out  the  ail-too  vivid  aniline  dyes.  In  various  passages, 
somewhat  neutralized  (we  think)  by  others,  Darwin  suggests 
the  view  which  many  of  his  disciples  hold  (sometimes  as  if  it 
were  their  own),  that  the  colours  and  patterns  of  animals 
are  outcrops  of  the  dynamic  constitution  of  the  creature, 
or  by-products,  it  may  be,  of  its  activity  ;  but  that  what 
happens  and  has  happened  in  Nature's  sifting  may  be 
described  as  an  elimination  of  the  fatally  exuberant  or 
conspicuous. 

The  Purpose  of  Youth. — As  we  ascend  the  scale  of 
animal  evolution,  we  find  that  one  of  the  tendencies,  most 
notable  in  Mammals,  is  to  lengthen  out  the  duration  of 
youth.  All  sorts  of  devices  and  precautions  conspire  to 
secure  that  the  young  animals  remain  longer  young — fed, 
protected,  freed  from  care  and  responsibilities,  dowered 
with  energy,  and  given  opportunity  to  play.  We  owe 
to  Groos,  in  particular,  the  idea  that  the  play-period  is  the 
educative  period  in  the  truest  sense,  and  of  fundamental 
importance  to  the  subsequent  life. 

We  have  discussed  the  matter  recently  in  our  Biology 
of  the  Seasons. 

'  There  are  many  play-instincts  among  animals  ;  they 
have  been  wrought  out  in  the  course  of  ages,  partly 


THE  CYCLE  OF  LIFE  409 

as  safety-valves  for  overflowing  energy,  partly  as  the 
muscular  correlates  of  emotion,  partly  as  opportunities 
for  the  emergence  of  variations  before  too  rigorous  selection 
begins,  but  mainly  as  periods  for  educating  powers  which 
are  essential  in  after-life.  Animals,  Groos  says,  do  not 
simply  play  because  they  are  young  ;  they  continue  young 
in  order  that  they  may  play.  For  play  is  the  young  form 
of  work,  and  the  animals  who  played  best  when  young, 
worked  best,  lived  best,  perhaps  loved  best,  when  they 
grew  up  '. 

In  his  Childhood  of  Animals  Dr.  Chalmers  Mitchell  has 
worked  out  the  important  thesis  that  the  purpose  of  youth 
is  to  give  time  for  the  breaking  down  of  rigid  instincts,  and 
their  replacement  by  actions  controlled  by  experience  and 
memory,  by  remembered  results  of  experiment.  We  would 
suggest  that  youth  is  the  time  when  co-ordinations  are 
established  between  the  instinctive  processes  of  the  lower 
brain-centres  and  the  intelligent  processes  of  the  cerebral 
cortex. 

It  is  plain  that  youth  is  a  perilous  time  ;  why  should  there 
be  this  tendency  to  lengthen  it  out  ?  The  answer  is  that 
it  is  the  time  for  self-expression.  The  number  of  brain-cells 
does  not  increase,  but  their  interlmkmgs  are  complexified, 
which  means  a  growth  of  intelligence  and  a  deepening  of 
feeling.  Thus  has  youth  been  justified  in  the  past ;  so  it  is 
justified  every  day. 

If  Natural  History  is  asked  to  give  hints  to  the  human 
educationist — and  stranger  things  have  happened — one  of 
them  will  be  this,  as  Chalmers  Mitchell  puts  it : — 

'  Youth  should  be  spent  in  blunting  [a  term  apt  to  be 
misunderstood  ?]  every  instinct,  in  awakening  and  stimu- 
lating every  curiosity,  in  the  gayest  roving,  in  the  wildest 


410  THE  WONDER  OF  LIFE 

experiment.  The  supreme  duty  of  youth  is  to  try  all 
things '. 

Finally  youth  passes  into  adolescence.  This  is  an  arc 
on  the  up-grade,  when  juvenile  characters  are  shed  and 
adult  characters  put  on.  There  is  a  final  acceleration  of 
growth  (with  correlated  rest  and  play,  and  plenty  of  food) ; 
there  is  internal  rearrangement  and  readjustment ;  there 
is  a  sifting  of  idiosyncrasies,  to  wit  variations ;  there  is  a 
criticism  of  that  acquired  veneer  which  we  call  modifications 
or  individually  acquired  characters ;  and  there  is  more 
than  a  beginning  of  sex-impulses. 

Courtship  among  Animals. — In  the  lower  reaches 
of  the  animal  kingdom  the  process  of  reproduction  is  often 
extraordinarily  wasteful.  Myriads  of  eggs  are  sown  broad- 
cast upon  the  waters,  and  millions  of  sperms  are  shed 
fortuitously.  Many  fishes  produce  several  millions  of  eggs, 
and  there  is  no  counting  spermatozoa.  Mr.  Oswald  H. 
Latter  has  given  a  vivid  description  of  the  discharge  of 
spermatozoa  from  the  male  freshwater  mussel.  It  may 
serve  to  illustrate  the  prodigal  wealth  of  reproductive 
material.  A  specimen  of  Unio  pictorum  emitted  from  the 
exhalant  aperture  between  the  shell- valves  a  fine  double 
cloud  of  milky  substance,  which  rose  nearly  to  the  surface 
of  the  water,  and  then  fell  as  a  diffused  cloud.  The 
whole  of  the  water  in  the  aquarium  became  cloudy 
and  the  emission  continued  for  some  hours.  It  appeared 
to  be  under  some  control,  for  a  slight  shaking  of  the  floor 
was  followed  by  a  cessation  of  the  streams  of  spermatozoa, 
though  the  ordinary  exhalant  current  of  water  appeared 
to  continue  without  interruption.  The  liberated  material 
consisted  of  myriads  of  sperm-balls,  revolving  and  swimming 
like  Vol vox-colonies,  and  finally  breaking  up  into  the 


THE   CYCLE  OF  LIFE  411 

component  spermatozoa.  These  exhibited  astonishing 
activity,  and  some  kept  it  up  below  a  cover-slip  for  seven 
hours  after  liberation. 

Many  of  the  lower  animals  feed  easily  and  have  much 
to  spare,  so  that  they  can  afford  to  be  prolific.  Moreover, 
until  the  nervous  system  reaches  a  certain  degree  of  integra- 
tion, the  sexes  cannot  be  definitely  aware  of  one  another. 
In  Echinoderms,  for  instance,  the  absence  of  ganglia  puts 
definite  sex-awareness  out  of  the  question.  At  many 
different  points,  however,  in  the  ascent  of  life  we  find 
economization  of  reproductive  material.  An  incipient  case 
is  familiar  in  the  salmon.  The  female  fish  makes  a  furrow 
in  the  gravelly  bed  of  the  river  and  lays  her  eggs  there. 
The  attendant  male  is  stimulated  by  the  presence  of  the 
mature  female  and  her  eggs,  and  liberates  the  sperms  or 
milt  along  the  furrow.  There  is  still  great  loss,  but  it  is 
the  beginning  of  an  improvement  upon  the  primitive  and 
wasteful  broadcast  semination  of  the  waters. 

Along  various  lines  of  animal  evolution  we  find  that  the 
males  and  females  have  become  very  definitely  aware  of 
one  another  and  are  excited  by  one  another.  There  is  a 
by-play  of  amatory  behaviour  preliminary  to  pairing,  and 
probably  rendering  the  pairing  more  effective.  A  pervasive 
excitement  may  change  the  creature's  character  and  appear- 
ance ;  the  whole  being  is  sometimes,  as  it  were,  transfigured. 
There  is  often  a  seeking  out  of  the  females  by  the  ardent 
males,  and  occasionally  there  is  an  appeal  made  to  the 
males  by  the  females.  The  excited  males  fight  with  one 
another,  sometimes  with  almost  maniacal  ferocity,  some- 
times in  a  half-playful,  bloodless  jousting.  Again,  in  a 
fascinating  variety  of  ways,  the  males  make  displays — of 
agility,  of  mettlesomeness,  of  beauty,  of  fragrance,  of 


4i2  THE  WONDER  OF  LIFE 

musical  talent,  and  so  forth — before   the  senses  of  their 
desired  mates. 

Mr.  W.  P.  Pycraft's  recently  published  charming 
volume  on  The  Courtship  of  Animals  gives  an  admirable 
discussion  of  the  whole  subject,  with  a  wealth  of  fresh  in- 
stances, and  we  shall  not  do  more  than  recall  a  few  pictures. 
Stag  fights  with  stag  till  they  drip  with  blood ;  the  rival 


FIG.  62. — Male  Spiders  (Zygoballus)  fighting.     (After  Prof,  and  Mrs. 
Peckham.) 

sea-lions  slash  with  their  great  canines  at  one  another's 
necks,  making  long  wounds,  as  the  scars  show  for  many  a 
day ;  the  cock  capercailzies  fight  in  the  early  spring  and 
the  snow  is  spotted  with  their  blood ;  the  blackcock's 
tournaments  at  dawn  are  revelations  of  mingled  passion 
and  pride  ;  the  polygamous  ruffs  fight  hour  after  hour  with- 
out wounds,  and  mingle  their  pugnacity  with  an  extra- 
ordinary self-abandonment ;  male  spiders  have  similarly 
bloodless  battles.  When  there  is  actual  elimination  of  the 


THE  CYCLE   OF  LIFE  413 

weak,  the  cowardly,  the  clumsy,  the  dull,  and  so  on,  so 
that  they  are  definitely  unsuccessful  or  less  successful  in 
reproduction,  the  combats  of  the  males  will  probably  have 
some  direct  evolutionary  influence,  as  Darwin  confidently 
believed.  But  there  is  great  need  for  a  stern  sifting  of  the 
data  and  an  accumulation  of  more. 

On  the  other  side,  there  is  the  great  variety  of  peaceful 


FIG.  63. — Male  spider  (Icius  mitratus)  dancing.     (After  Peckham.) 

ways  in  which  male  animals  give  expression  to  their  emotions 
in  the  presence  or  proximity  of  their  desired  mates.  Many 
male  spiders  have  a  characteristic  love-dance,  differing 
for  different  species,  in  which  they  appear  to  our  eyes  as 
if  they  were  showing  off  their  good  points.  Some  insects 
have  luminous  love-signals,  many  offer  up  fragrant  incense, 
many  give  themselves  up  to  energetic  serenading — if  we 
may  so  call  it  in  our  almost  complete  absence  of  knowledge 
in  regard  to  the  sense  of  hearing  in  insects.  Many  birds 
make  elaborate  displays,  bending  and  bowing,  strutting 
and  saluting,  circling  and  fluttering  ;  and  even  a  few  of  the 


414  THE  WONDER  OF  LIFE 

cold-blooded  fishes  and  newts  have  their  love-play.  Finest 
and  most  familiar  is  the  musical  appeal  of  many  birds. 

Thousands  of  interesting  facts  are  known  as  to  visible 
behaviour,  but  it  is  difficult  to  judge  of  the  inward  spirit. 
We  must  not  be  recklessly  generous,  nor  materialistically 
sceptical.  The  whole  life  is  one,  and  while  we  know  that 
internal  secretions  or  hormones,  liberated  at  the  breeding 
season  and  pervading  the  whole  body,  influence  the  brain 
and  the  whole  nervous  system,  and  the  circulation  of  the 
blood  and  its  composition,  we  are  not  on  that  account  tc 
suppose  that  the  bird  on  the  bough  is  emotionless,  like  a 
musical  box.  We  must  not  read  too  much  into  the  displays, 
for  the  suitors  are,  as  it  were,  sex-intoxicated,  expressing 
their  ardour  instinctively  and  with  abandon,  rather  than 
with  deliberation  or  strategy,  but  we  must  not  think  of 
them  too  cheaply,  as  if  they  expressed  lust  only,  and  no 
love. 

As  to  the  evolutionary  importance  of  the  courtship 
behaviour,  there  is  need  at  present  for  a  critical  revision  of 
the  data.  The  late  Alfred  Russel  Wallace  always  insisted, 
thus  differing  from  Darwin,  that  there  was  little  convincing 
evidence  that  the  female  bird  chooses  her  partner,  or  chooses 
him  because  of  any  particular  excellence  in  colour  or 
plumage,  agility  or  musical  talent ;  but  some  good  ornithol- 
ogists bring  forward  circumstantial  cases  of  unattractive 
male  birds  being  left  unmated.  More  facts  are  needed. 
While  Darwin  seemed  sometimes  to  credit  the  females  with 
a  high  degree  of  taste  or  aesthetic  fastidiousness,  he  was 
probably  on  safer  ground  when  he  wrote  :  '  It  is  not  probable 
that  she  consciously  deliberates ;  but  she  is  most  excited 
or  attracted  by  the  most  beautiful  or  melodious  or  gallant 
males '.  The  probability  is  that  the  female  surrenders 


THE   CYCLE  OF  LIFE  415 

herself,  not  to  a  male  selected  because  of  some  particular 
excellence,  but  to  the  fortunate  fellow  whose  ensemble  most 
successfully  excites  her  sexual  interest.  Now,  if  this  be  so, 
and  if  a  number  of  uninteresting  males  are  definitely 
unsuccessful  or  less  successful  in  reproduction,  there  will  be, 
in  some  measure,  a  denning  of  the  path  of  evolution.  There 
will  be  not  only  a  toleration,  but  a  favouring  of  beauty ; 
there  will  be  at  least  a  handicapping  of  dullness. 

Looking  over  a  treasury  of  illustrations,  such  as  Mr. 
Pycraft's  Courtship  of  Animals  contains,  we  cannot  but 
ask  what  the  deep  significance  of  the  whole  elaborate  system 
of  behaviour  may  be,  for  it  is  not  enough  to  say  that  it  is 
simply  an  overflow  of  vital  energy  and  joie  de  vivre.  The 
persistence  of  a  race  depends  on  the  success  with  which  it 
continues  its  kind,  and  the  sex-impulse  with  its  urge  has 
made  reproduction  a  certainty.  The  instinctive  behaviour 
of  courtship  has  added  to  the  force  and  subtlety  of  the 
overmastering  internal  sex-impulse.  Indeed,  as  Emerson 
said,  the  sex-impulse  is  imperious  so  that  reproduction 
may  be  ensured.  As  a  matter  of  fact,  we  should  turn  the 
idea  round  a  little,  and  say  that  those  types  have  survived 
in  which  the  sex-impulse  was  strong  ;  but  it  comes  to  the 
same  thing.  Groos  has  pointed  out  that  coyness  on  the 
female's  part  is  a  character  of  considerable  racial  value, 
and  the  courtship  allows  of  coyness  because  the  fittest  males 
succeed  in  overcoming  it.  Our  general  conclusion  is  that 
the  deep  significance  of  courtship-behaviour  is  that  it 
makes  pairing  more  effective. 

IN  ILLUSTRATION. 

Sea  Lions. — In  Spring  a  few  old  male  sea-lions  make 
their  appearance  at  the  Pribylov  Islands  and  swim  about 


416  THE  WONDER   OF  LIFE 

for  several  days,  prospecting.  They  examine  the  '  rookery ' 
and  go  off  to  sea  again,  returning  in  reinforced  numbers. 
Each  male  chooses  a  spot — some  thirty  yards  square — for 
his  future  harem,  and  jealously  guards  it  against  intruders. 
About  two  months  later  the  females,  who  are  not  nearly  so 
large  as  the  males,  appear  on  the  scene,  and  there  is  great 
competition  for  them,  each  '  polygamous  sultan '  trying 
to  secure  from  fifteen  to  twenty  wives.  Accounts  differ  a 
good  deal  as  to  the  degree  of  '  give  and  take  '  among  rival 
males.  The  cubs  are  born  a  few  days  after  the  arrival  of  the 
mothers,  and  seem  to  require  a  good  deal  of  education. 
Soon  after  the  birth  of  the  young,  Professor  D'Arcy 
Thompson  tells  us,  '  the  comparative  quiet  of  the  rookery 
is  exchanged  for  a  babel  of  noise  and  incessant  quarrelling.' 
The  old  males  try  to  add  to  the  score  or  so  of  wives  they 
have  apiece ;  the  wifeless  younger  males  try  to  secure 
mates  ;  there  are  great  fights  among  rival  bullies.  '  So 
all  day  long  the  noise  of  battle  rolls  along  the  beaches 
by  the  wintry  sea,  and  the  growling  and  the  snarling, 
the  confusion  and  the  din,  are  for  some  weeks  together 
indescribable  '.  The  younger  males,  or  bachelors,  herd  apart 
from  the  others,  and  both  they  and  the  married  females 
go  down  to  the  sea  to  feed.  It  is  noteworthy,  on  the 
other  hand,  that  '  the  old  males  starve  rather  than  leave 
their  posts ;  they  come  fat  and  vigorous  in  springtime, 
and  are  gaunt,  emaciated,  and  scarred  with  the  scars  of 
many  battles  before  they  leave  again  in  autumn '. 

Fragrance. — In  many  butterflies,  such  as  the  green- 
veined  white  (Ganoris  napi),  the  males  have  a  distinct 
flowery  perfume,  which  is  associated  with  remarkable 
'  plume  scales '  on  the  upper  surface  of  the  wings.  It  is 
readily  perceptible  if  we  rub  the  wings  with  a  camel-hair 


THE   CYCLE   OF  LIFE  417 

brush.  Similar  perfumes,  almost  always  flower-like,  are 
well  known  in  relatives  of  the  common  whites,  and  they  are 
almost  invariably  confined  to  the  males  and  to  the  upper 
surface  of  the  wings.  The  cells  that  produce  the  scent — 
which  may  be  of  the  nature  of  a  volatile  oil — seem  to  lie 
in  the  skin  (or  hypodermis)  below  the  surface-membrane 
of  the  wing,  and  the  '  plume  scales  '  are  only  distributors. 
There  can  be  little  doubt  that  Fritz  Miiller's  suggestion 
is  correct,  that  the  pleasant  flower-like  scents  are  useful  to 
the  males  in  their  courtship  of  the  females,  as  auxiliary 
means  of  attraction.  It  may  also  be  that  they  help  mem- 
bers of  the  same  species  to  recognize  one  another,  for  the 
perfumes  are  often  exceedingly  distinctive  or  specific. 
As  to  the  repulsive  scents,  there  is  definite  evidence  that 
they  help  to  protect  their  possessors  from  insect-eating 
enemies. 

Fire -Flies. —We  have  already  referred  to  the  court- 
ship of  the  Italian  Fire-fly.  The  female,  sitting  among 
the  grass,  signals  to  passing  males,  who  respond  and 
settle  down  around  her  in  a  devoted  circle.  Flashes 
of  light  pass  from  the  suitors  to  the  object  of  their  desire, 
and  from  her  to  them,  till  the  fire  is  sufficiently  fanned, 
a  pairing  takes  place,  and  the  party  breaks  up.  Not  less 
refined  is  the  approach  that  some  male  spiders  make  to 
their  somewhat  explosive  mates — vibrating  with  one  of 
their  appendages  one  of  the  threads  of  the  web  on  which 
the  exquisitely  sensitive  spinner  sits. 

Audible  Signals. — Dr.  Karl  Peters  has  given  us  a  very 
interesting  picture  of  love-signalling  on  the  part  of  an 
Alpine  moth  (Endrosa  or  Setina  aurita,  var.  ramosa),  which 
he  studied  at  Arolla.  The  males  fly  about  actively,  but 
the  females  are  sluggish  and  rest  for  the  most  part  on 


418  THE   WONDER  OF  LIFE 

tussocks  of  grass,  where  they  are  very  inconspicuous.  The 
males  are  able  to  produce  a  crackling  or  snapping  sound, 
and  it  seems  as  if  the  females  responded  to  this  signal  by 
vibrations  of  their  body  and  wings.  When  the  males 
fly  overhead  or  settle  down  in  the  vicinity,  the  females 
make  themselves  more  conspicuous  by  their  tremulous 
movements,  which  appear  to  attract  the  male's  attention. 
When  the  sound  stops,  the  answering  movement  stops. 
Even  when  the  female  cannot  see  the  male,  she  answers 
back  when  the  sound  begins.  It  seems,  then,  as  if  the  male's 
signal  appealed  to  a  hearing  organ  and  the  female's  signal 
to  sight.  Dr.  Peters's  observations  are  of  great  interest, 
because  the  experiments  that  have  been  made  to  test  the 
auditory  powers  of  insects  have  been  very  unsatisfactory. 
It  is  difficult  to  believe  that  the  instrumental  music  of 
Cicadas  and  crickets  falls  on  deaf  ears,  but  the  experiments 
testing  this  are  inconclusive.  Insects  that  have  been 
credited  with  the  power  of  hearing  remain  quite  indifferent 
to  a  great  variety  of  sounds,  but  it  is  possible  that  the 
experiments  fail  because  the  sounds  used  as  tests  have 
been  meaningless  and  therefore  quite  uninteresting  to  the 
insects.  More  observations  like  those  of  Dr.  Peters  are 
much  to  be  desired. 

Puzzles  of  Behaviour. — The  Praying  Mantis,  or  Prego- 
Dieu  of  the  Proven9als,  is  a  ferocious  Carnivore  in  a  vege- 
tarian order  (Orthoptera),  and  feeds  exclusively  on  living 
victims,  such  as  crickets,  which  it  seizes  by  the  back  of  the 
neck.  Fabre  has  shown  that  in  comfortable  captivity, 
with  abundant  food,  the  mature  females  fight  fiercely 
and  devour  one  another.  The  males  likewise,  smaller 
and  more  delicate  than  the  females,  are  often  devoured 
by  their  mates,  after  having  had  their  addresses  accepted. 


THE   CYCLE   OF  LIFE  419 

'  In  the  course  of  two  weeks,'  Fabre  writes,  '  I  have  seen 
the  same  Mantis  treat  seven  husbands  in  this  fashion. 
She  admitted  all  to  her  embraces,  and  all  paid  for  the 
nuptial  ecstasy  with  their  lives  '.  But  we  must  remember 
that  these  same  female  Mantises  make  a  beautiful  and 
elaborate  cradle  for  the  eggs,  beating  up  a  somewhat  silken 
secretion  into  a  spongy  foam  which  hardens  in  the 
air. 

The  same  mysterious  '  post-matrimonial  cannibalism  '  is 
illustrated  by  some  scorpions  and  spiders,  by  some  crickets, 
and  by  the  so-called  '  golden '  Scarabee  beetle.  It  must 
be  remembered,  however,  that  most  of  the  records  relate 
to  creatures  in  captivity.  Fabre  relates  in  regard  to  the 
'  golden  Scarabaeus,'  which  does  such  good  work  in  destroy- 
ing caterpillars  that  creep  on  the  ground,  such  as  the  pro- 
cession caterpillar,  that  between  the  middle  of  June  and 
the  first  of  August,  twenty-five  comfortably- cased  Scarabees 
were  reduced  to  five — all  females.  He  saw  one  of  the 
females  devouring  a  male,  and  he  found  that  all  the  corpses 
of  the  males  had  been  eviscerated.  The  fact  that  the 
males  did  not  seem  to  resist,  suggests  that  they  may  be 
naturally  moribund  after  mating. 

Parental  Care  and  the  Family. — In  many  animals, 
from  worm  to  frog,  the  mother  discharges  a  large  number 
of  eggs,  and  leaves  them  to  develop.  Sometimes, 
indeed,  as  in  some  marine  worms  and  in  many  butterflies 
and  moths,  she  dies  soon  after  reproduction.  Even  in 
strong  animals  like  lampreys  and  eels,  death  seems  to 
follow  like  a  nemesis  close  on  the  heels  of  reproduction. 
It  must  be  admitted  that  the  liberation  of  huge  numbers 
of  ova — sown  broadcast  in  the  waters — is  a  wasteful  pro- 
cess. There  is  great  mortality  and  many  of  the  eggs  are 


420  THE  WONDER   OF  LIFE 

not  even  fertilized.  The  race  is  continued  because  there 
are  so  many. 

One  must  never  think  of  Nature  as  deliberating  and 
deciding  to  replace  a  wasteful  process  by  a  more  economical 
one,  nor  yet  as  simply  drawing  her  bow  at  a  venture  and 
in  the  course  of  time  hitting  a  mark.  What  goes  on  is 
a  ceaseless  experimenting  in  different  modes  of  self- 
expression.  Less  prolific  forms  arose,  and  those  that  in- 
stinctively took  some  care  of  eggs  or  offspring  tended  to 
define  the  direction  of  evolution.  Sometimes,  on  the  other 
hand,  more  careful  types  arose — resting  exhausted  beside 
their  mass  of  eggs,  and  by  and  by  incubating  them — and 
those  that  were  more  economical  in  productivity  would 
tend  to  define  the  direction  of  evolution.  The  process 
may  have  worked  either  way. 

A  number  of  suggestions  may  be  offered.  (1)  The 
passage  from  aquatic  to  terrestrial  life  is  associated  with 
internal  fertilization  and  with  the  suppression  of  larval 
stages  (see  Chapter  II),  and  it  follows  that  the  mother 
animals  would  come  to  have  a  longer  organic  acquaintance 
with  their  ova.  The  bird  laying  her  eggs  is  much  more 
aware  of  what  she  is  doing  than  the  fish  in  the  sea.  (2) 
In  certain  conditions,  such  as  the  low  temperature  of  the 
abysses  or  of  polar  seas,  growth  processes  are  slowed.  This 
might  lead  to  a  longer  retention  of  the  ova  within  the  body, 
and  to  viviparity.  It  is  very  significant  that  in  Antarctic 
Echinoderms,  for  instance,  there  is  a  general,  though  not 
complete  suppression  of  free-swimming  larval  stages,  and 
many  cases  are  known  of  parental  care,  differing  curiously 
in  details.  (3)  As  is  usual,  when  we  face  such  problems, 
we  find  that  there  are  many  approaches  to  parental  care 
and  family  life.  The  goal  was  probably  reached  very 


THE   CYCLE   OF  LIFE  421 

gradually  and  by  various  routes.  Thus  we  see  a  beginning 
in  those  cases  in  which  the  mother  lays  her  eggs,  instead 
of  merely  liberating  them.  The  female  salmon  lays  eggs 
in  a  furrow  which  she  makes  in  the  gravelly  bed  of  the 
stream.  We  see  a  beginning  in  those  cases  in  which  the 
mother  carries  her  eggs  about  with  her  after  she  has  liberated 


FIG.  64. — Female  Spider — Dolomedes  mirabilis — carrying  underneath 
her  body,  attached  by  silk  threads,  the  silken  cocoon  containing 
the  eggs  and  eventually  the  young  spiders.  (After  Blackwall.) 


them.  Many  a  spider  has  a  silken  cocoon  which  she  bears 
about  with  her  until  the  spiderlings  hatch.  We  see  a 
beginning  in  the  retention  of  the  eggs,  not  only  until  they 
become  larvae,  but  until  particular  circumstances  arise. 
Thus  the  freshwater  mussel,  which  we  have  discussed, 
keeps  its  Grlochidia  in  its  gill-cradle  until  a  minnow  or 
the  like  comes  conveniently  into  the  vicinity.  We  see 
a  beginning  in  the  way  many  an  animal  mother  allows  her 
young  ones  to  clamber  about  her  body,  holding  on  to  her 
and  being  protected  by  her.  The  generalization  may  be 


422 


THE  WONDER   OF  LIFE 


ventured,  that  the  maternal  care  is  in  certain  respects  like 
an  external  continuation  of  the  internal  organic  linkage. 

Paternal  Care. — Some  of  the  backboneless  animals 
which  show  parental  care  are  hermaphrodites.  This  is 
true  of  the  brook-leech  (Clepsine),  which  carries  about  its 
young  ones  on  the  under  surface  of  its  body.  In  other 
cases,  both  of  high  and  low  degree,  the  parental  care  is 


FIG.  65. — Sea  Horses,  Hippocampus.  The  upper  row  shows  the  success- 
ive positions  of  the  body  in  swimming.  The  body  bends  forwards 
and  straightens  again.  The  lower  row  shows  the  fishes  at  rest.  ( After 
Anthony  and  Chevroton.) 

exhibited  by  the  males.  We  find  this  among  those  inter- 
esting animals,  of  uncertain  zoological  position,  known  as 
sea-spiders  or  Pycnogonids,  where  the  males  carry  the  eggs 
attached  to  two  of  their  legs.  We  find  it  in  several  fishes, 
such  as  the  stickleback,  who  makes  and  guards  the  nest 
among  the  sea- weed,  or  the  sea-horse  (Hippocampus),  who 


THE   CYCLE   OF  LIFE  423 

carries  the  eggs  about  in  his  breast-pocket.  The  same 
is  true  of  some  pipe-fishes  (Syngnathus). 

Somewhat  like  the  stickleback's  nest,  but  made  by  the 
female,  is  that  of  the  kelp-fish  (Heterotrichus  rostrata)  of 
the  South  Carolina  kelp-beds.  Mr.  C.  H.  Holder  observed  a 
female  in  captivity,  and  saw  her  push  her  way  through  and 
round  a  bunch  of  seaweed,  depositing  a  white  viscid  cord, 
which  clung  to  the  fronds,  and  bore  numerous  minute  white 
eggs.  The  male,  who  is  brilliantly  coloured  at  the  breeding- 
season,  like  the  kelp  and  like  his  mate  at  other  seasons, 
mounted  guard  over  the  '  nest ',  while  the  female  rested. 
The  whole  process  took  a  couple  of  hours,  and  the  result 
was  a  globular  white  mass  about  the  size  of  a  hen's  egg. 
Of  the  sculpin  (Myoxocephalus  scorpius),  a  common  shore- 
fish  of  northern  seas,  Dr.  Theodore  Gill  relates  that  the 
male  may  make  a  rough  nest  of  seaweeds  and  pebbles  for 
the  reception  of  the  spawn,  and  that  he  mounts  guard  over 
the  mass  of  eggs,  clasping  it  with  its  fins  for  a  long  time. 

In  the  case  of  Arius  fissus,  a  shore  fish  from  French  Guiana, 
about  twenty  eggs  ripen  at  one  time.  When  these  are  laid, 
the  male  takes  them  into  his  mouth,  where  they  remain 
until  after  hatching,  until,  in  fact,  the  yolk  sac  is  absorbed. 
During  the  whole  of  this  incubation  period  the  father  fish 
is  condemned  to  fast,  so  that  we  have  a  somewhat  whimsical 
instance  of  that  antithesis  between  nutrition  and  repro- 
duction which  echoes  through  life. 

Among  Amphibians  there  are  many  cases  parallel  to 
those  which  occur  among  fishes.  Thus  the  male  nurse- 
frog  (Alytes),  not  uncommon  in  some  parts  of  the  Continent, 
carries  the  strings  of  ova  on  his  back  and  about  his  hind 
legs,  buries  himself  in  the  damp  earth  until  the  development 
of  the  embryos  is  approaching  completion,  then  plunges 


424 


THE  WONDER   OF  LIFE 


into  a  pool,  where  he  is  freed  from  his  living  burden.  In 
the  case  of  the  Surinam  toad  (Pipa),  the  male  is  said  to 
help  the  female  in  placing  the  eggs  upon  her  back,  where 
each  sinks  into  a  little  skin  pocket,  in  which  it  develops 
without  passing  through  a  tadpole  stage.  In  Nototrema 
the  female  has  a  dorsal  pouch  opening  backwards,  and  into 
this  the  male  pushes  the  eggs  with  his  hind  legs.  In  a 
little  South  American  frog,  Darwin's  Rhinoderma,  the 
male  carries  the  (5-15)  ova  in  his  croaking-sacs,  which 
become  enormously  enlarged  in  the  course  of  their  develop- 
ment. Eventually  miniature  frogs  jump  out  of  the  father's 
mouth  !  In  a  number  of  birds  the  incubation  is  shared 
by  both  sexes ;  in  the  American  ostrich  (Rhea)  it  is  said 
to  be  wholly  discharged  by  the  male. 

When  we  see  the  male  lumpsucker  or  cock-pa  idle 
(Cyclopterus)  mounting  guard  over  the  mass  of  eggs  in 
the  rock-pool,  and  keeping  them  clean  and  aerated  by 
frequent  agitations  of  the  water,  and  continuing  at  this 


FIG.  66.—' 


•The  Lumpsucker  (Cydopterua  lumpus).     From  a  specimen. 


THE   CYCLE  OF  LIFE  425 

task  for  many  days,  we  are  undoubtedly  face  to  face  with 
parental  care,  and  we  are  surprised  that  it  should  be  pater- 
nal. Two  suggestions  may  be  offered: — (1)  that  just  as 
maternal  care,  in  certain  of  its  expressions,  may  be  thought 
of  as  a  sort  of  prolongation  of  viviparity,  so  paternal  care 
may  be  organically  associated  with  sex-instincts ;  and 
(2)  that  just  as  we  find  a  female  reindeer  always  with 
antlers  and  the  female  Red-necked  Phalarope  with  mascu- 
line colouring  and  ways,  so  parental  instincts  which  usually 
develop  only  in  the  females  may,  to  suit  particular  needs, 
be  grafted  on  to  the  males. 

There  is  not  much  parental  care  among  Gasteropods, 
but  there  are  often  very  remarkable  egg-cases  in  which  the 
early  stages  of  development  are  passed.  We  may  refer  in 
illustration  to  the  American  Slipper  Limpet  (Crepidula 
fornicata),  which  has  spread  rapidly  since  1880  on  British 
oyster  grounds.  It  takes  special  care  of  its  spawn,  as 
Mr.  Orton  has  told  us. 

'  It  constructs  about  fifty  to  sixty  membranous  bags, 
into  each  of  which  it  passes  about  two  hundred  and  fifty 
eggs,  and  as  the  bags  are  made  and  filled  with  eggs,  they 
are  closed  and  fastened  together  by  short  cords.  These 
cords  are  finally  all  stuck  on  to  the  surface  on  which  the 
slipper-limpet  happens  to  be  sitting,  so  that  when  by  taking 
away  the  spawning  individual  the  spawn  is  uncovered,  it 
looks  like  a  bundle  of  balloons,  each  containing  a  number 
of 


Fabre  has  described  in  his  inimitable  manner  the  be- 
haviour of  a  Hymenopterous  insect,  the  Bee-hunter 
(Philanthus  apivorus),  which  pursues  the  hive-bee.  It 
always  stings  the  bee  on  a  minute  soft  patch  in  the 
throat,  which  leads  the  sting  into  the  cervical  ganglia, 


426  THE  WONDER  OF  LIFE 

'  abolishing  life  at  a  single  blow  '.  There  is  a  much  larger 
soft  area  further  back,  but  that  is  not  utilized.  It  is  a 
knock-out  blow  under  the  chin  that  is  delivered.  Clasping 
its  dead  victim  firmly,  the  Philanthus  squeezes  out  the 
honey  from  the  stomach,  and  does  so  repeatedly  till  every 
drop  is  enjoyed.  The  fresh  corpse  of  the  bee  is  then  given 
by  the  Philanthus  to  her  grubs,  to  whom  the  honey  is 
noxious ! 

In  many  insects  the  mothers  exert  themselves  unsparingly 
to  provide  stores  of  food  for  the  young,  but  participation 
on  the  father's  part  is  very  rare.  Among  the  dung-rolling 
beetles  there  are  exceptions — such  as  the  Sisyphus,  the 
males  and  females  of  which  work  together  in  kneading  a 
pill  of  dung  and  transporting  it,  over  great  difficulties,  to 
the  underground  burrow  where  the  eggs  are  laid.  In  the 
case  of  the  scarabee,  Fabre  tells  us  that  while  the  sexes 
co-operate  in  rolling  balls  of  dung  for  their  own  consumption, 
the  female  is  left  to  do  all  the  work  of  moulding  the  ball 
and  transporting  it  when  it  is  for  the  use  of  the  future 
brood. 

In  non-social  as  well  as  social  insects,  parental  care  is 
sometimes  exhibited.  The  quaint  mole-crickets  (Gryllo- 
talpa)  move  their  eggs  in  their  underground  nests  according 
to  the  weather,  and  guard  them  sedulously  against  black- 
beetles  and  the  like.  The  earwig  sits  on  her  eggs,  and  older 
writers  have  described  what  some  who  have  recently 
watched  earwigs  carefully  have  failed  to  confirm,  that  the 
mother-insect  gathers  her  young  under  her  as  a  hen  her 
chickens.  In  spite  of  Fabre's  criticism,  it  seems  likely 
that  De  Geer  was  accurate  in  his  description  of  the  mother 
birch-bug  brooding  over  her  eggs  and  young. 

F.  P.  Dodd  describes  the  brooding  habits  of  one  of  the 


THE  CYCLE  OF  LIFE  427 

bugs,  Tectocoris  lineola,  var.  banksi.  The  mother  sits  in  a 
brooding  attitude  over  her  eggs  for  three  weeks,  until  the 
young  are  hatched  out.  She  does  not  have  anything  to 
eat  during  these  weeks.  When  the  young  begin  to  break 
through  the  egg-shells,  the  mother  backs  away  for  an 
inch  or  so  from  off  the  egg-mass,  and  remains  there  for 
some  hours,  long  after  the  last  egg  is  hatched.  She  then 
departs,  leaving  the  young  bugs,  whom  she  has  perhaps 
saved  from  Ichneumon  flies,  to  fend  for  themselves. 

It  is  among  birds  and  insects  that  we  find  the  highest 
development  of  parental  care,  but  what  a  contrast  there  is 
between  the  two  expressions.  Among  insects  the  prepara- 
tions that  are  made  for  the  young  are  for  the  most  part 
instinctive,  and  the  mother  is  often  without  the  satisfaction 
of  even  seeing  her  offspring — for  she  is  dead  before  her  eggs 
are  hatched.  Among  birds,  while  instinctive  behaviour 
continues,  it  is  associated  with  much  more  intelligence, 
and  the  preparation  of  nest-making  is  followed  up  by  the 
patience  of  brooding,  and  that  again  by  often  prolonged 
nurture,  and  even  education.  Many  birds  are  careful  in 
turning  their  eggs  and  in  keeping  the  nest  clean  after  the 
young  ones  are  hatched.  Of  the  nests  of  birds,  what  shall 
we  say? — so  many  of  them  express  a  climax  of  art  (both 
intelligent  and  instinctive)  on  the  one  hand  and  of  instinc- 
tive altruism  on  the  other.  For  artistic  quality,  take  the 
nest  of  the  wren,  of  the  thrush,  of  the  chaffinch,  of  the 
house-martin,  of  the  bottle  titmouse,  of  the  tailor-birds, 
and  of  the  weaver-birds.  Or  consider  the  single  case  of 
the  sea-swift,  which  achieves  the  impossible  by  fashioning 
a  firm  nest  out  of  the  juice  of  its  mouth.  For  altruistic 
quality,  take  MacGillivray's  fact  that  he  got  2,379  feathers 
out  of  the  nest  of  the  long-tailed  tit,  or  the  burrowing  of 


428 


THE  WONDER  OF  LIFE 


the  sand-martin — an  activity  so  alien  to  a  bird's  nature — 
or  the  labour  of  several  months  that  is  spent  in  building, 
pellet  by  pellet,  the  strong  two-chambered  mud-nest  of 
the  S.  American  oven-bird — an  architectural  masterpiece 
that  may  be  as  big  as  a  child's  head. 

The  brooding  must  imply 
a  good  deal  of  a  quality 
allied  to  patience,  and  in 
many  cases  not  a  little  of 
a  quality  allied  to  courage 
— when  an  enemy  comes 
nosing  all  round  about  the 
nest.  The  shy  curlew  has 
been  known  to  allow  a 
photographer  to  bring  a 
large  camera  within  ten 
feet  of  her  nest  without 
betraying  herself  by  the 
slightest  movement.  In 
some  cases,  e.g.  of  great 
heat,  the  brooding  bird 
.  appears  to  suffer  consider- 
ably, and  perhaps  this  has 


FIG.  67. — An  Emperor  Penguin, 
Aptenodytes  forsteri,  with 
the  young  one  on  her  feet. 
(After  Wilson.) 


something  to  do  with  the 
fact  that  birds  almost  always 
nest  in  the  coldest  part  of 
their  migratory  range.  The 
bird  has  to  do  all  this,  but  the  same  may  be  said  of  much 
of  the  parental  care  which  all  the  world  admires  in  the 
human  mother  —  it  is  instinctive.  In  Man  there  is 
probably  greater  possibility  of  disobedience  and  there  is 
a  fuller  awareness  of  what  it  all  means. 


THE   CYCLE  OF  LIFE  429 

After  brooding  there  is  the  labour  of  feeding  the  young, 
which  often  taxes  to  the  utmost  the  energies  of  both  parents. 
Miles  away  from  the  Bird-Berg,  where  tens  of  thousands  of 
guillemots  lay  their  eggs  on  the  ledges  of  the  cliffs,  there 
is  a  '  bank '  where  sand-eels  abound,  and  it  is  interesting 
to  lie  in  a  boat  and  see  the  constant  double  stream  of  birds 
passing  overhead,  all  those  returning  to  the  cliffs  having 
a  glistening  fish  in  their  mouth.  We  do  not  know  which 
most  to  wonder  at,  the  appetite  of  the  youngsters,  the 
indefatigableness  of  the  parents,  or  the  supply  of  sand- 
eels. 

We  have  already  referred  to  the  story  of  the  hornbill. 
The  mother-bird  nests  in  a  hole  in  a  tree,  and  is 
imprisoned  by  a  doorway  of  resinous  material,  big 
enough  to  let  the  male  bird's  bill  in ,  but  small  enough 
to  keep  enemies  out.  On  the  male  devolves  the  task 
of  procuring  food  for  his  immured  mate,  and  afterwards 
for  his  offspring  also.  After  three  weeks  of  it,  he  is  often 
worn  quite  thin,  and  sometimes  he  actually  succumbs  to 
his  other-regarding  exertions  before  he  is  rejoined  by 
the  female  bird.  He  has  to  do  it — and  it  is  said  that  an 
unrelated  male  will  attend  to  a  widowed  bird — so 
that  we  may  not  be  warranted  in  using  big  words  like 
altruism  in  appreciating  his  behaviour.  But  no  amount 
of  scrupulosity  can  disguise  the  fact  that  his  expenditure 
of  energy  is  not  for  himself. 

After  the  labour  of  feeding,  comes  the  fine  art  of 
education,  for  the  young  bird  has  always  a  great  deal 
to  learn.  Experiments  in  artificial  incubation  have  shown 
conclusively  that  the  young  bird  is  not  rich  in  inborn 
knowledge.  The  chick  artificially  hatched,  with  the  aid  of 
an  inanimate  foster-mother,  has  no  instinctive  recognition 


430  THE  WONDER  OF  LIFE 

of  its  actual  mother's  cluck.  Even  when  thirsty  it  does 
not  recognize  water  as  drinkable  stuff,  not  even  when  it 
walks  through  it.  So  unprejudiced  is  its  tabula  rasa  of  a 
brain,  that  it  will  stuff  its  crop  with  worms  of  red  worsted. 
But  the  point  is  that  it  makes  up  for  its  paucity  of  instincts 
by  an  extraordinarily  rapid  educability.  And  that  is 
what  the  parent-birds  work  with  in  educating  their  young 
in  the  ordinary  conditions  of  wild  nature. 

As  all  Mammals  except  the  primitive  Monotremes  are 
viviparous,  their  exhibition  of  parental  care  is  perhaps  not 
so  striking  as  in  the  nest-building  and  brooding  birds,  but 
it  often  reaches  a  high  level.  We  have  to  remember  the 
often  prolonged  gestation — the  mother  carrying,  as  it  were, 
a  huge  parasite  within  herself,  the  suckling  of  the  young, 
and  it  may  be  carrying  them  about,  as  in  Marsupials  and 
Bats,  the  defence  of  the  family,  and  their  initiation  into 
the  business  of  life.  Some  Mammals,  such  as  monkeys, 
have  a  prolonged  infancy  and  a  long  gastric  education  on 
milk ;  others  are  quickly  able  to  look  after  themselves. 
We  read  that  a  giraffe  is  able  to  stand  up  in  about  twenty 
minutes  after  birth,  to  run  freely  in  a  day  or  two,  and  to 
nibble  grass  in  three  weeks. 

Chain  of  Parental  Instincts. — There  are  many  unsolved 
problems  connected  with  parental  care,  but  we  think  that 
Professor  F.  H.  Herrick  has  made  many  points  clearer  by  his 
conception  of  a  chain  or  cycle  of  parental  instincts,  to 
which  we  have  already  referred  in  connection  with  the 
cuckoo  (p.  320).  The  events  in  the  cycle  follow  one 
another  with  almost  clock-like  precision,  but  are  always 
liable  to  be  influenced  by  intelligence.  Normally  they 
form  a  harmonious  series,  and,  what  is  very  important, 
there  is  an  attunement — a  time-keeping — between  the 


THE  CYCLE   OF  LIFE  431 

instincts  of  the  parents  and  those  of  the  offspring.  In- 
dividual disturbances  of  the  harmony  or  attunement  are 
continually  occurring,  and  are  often  misinterpreted  as 
insoluble  puzzles.  In  the  cuckoos  and  cow-birds  a  remark- 
able change  in  instincts  has  been  evolved  as  a  modus 
vivendi  to  meet  a  disturbance  of  the  time-keeping. 

We  give  a  shortened  statement  of  Herrick's  analysis  of 
the  reproductive  cycle. 

1.  The  spring  migration  to  the  breeding  area  or  birth- 
place. 

2.  Courtship  and  mating,  often  attended  by  song  and 
dance,  especially  in  the  male. 

3.  Nest-building  : — (a)  selecting  a  site  or  using  an  old 
one ;     (6)  building  the  nest  or  adapting  an  old  one. 

4.  Egg-laying,  usually  at  daily  intervals  in  the  completed 
nest.    As  in  (3),  this  is  often  attended  by  instincts  of 
guarding,  fighting  and  concealment. 

5.  Incubation  or  brooding  instinct ;    attended  as  before 
by  instincts  of  guarding,  fighting  and  concealment ;   often, 
as  it  proceeds,  allaying  all  fear  ;   including  a  variety  of 
instinctive  acts,  sometimes  recurrent,  as  removal  of  eggs 
in  bill,  inspection  of  eggs,  stirring  of  eggs  with  bill  or  feet, 
cleaning  nest  by  removal  of  broken  eggs  or  shells,  shielding 
eggs  from  heat  or  cold,  and  sometimes  hiding  them  with 
covering  of  wings. 

PAKENT.  YOUNG. 

6.  Care   of  the   young —         Initial  responses  at  and 
collecting  food  ;  feeding  the  after  hatching  ;   swallowing 
young  ;   inspecting  the  nest  reflexes  ;     call    notes,    and 
and     nestlings ;       cleaning  later  alarm  notes ;   burrow- 
both  •    etc.  ing  under  old  bird;    etc. 


432  THE  WONDER  OF  LIFE 

7.  Care  and  '  education  '  Flight,  fear,  seeking  prey, 
of  young,  guarding,  fighting  giving  call  and  alarm  notes  ; 
for,    feeding,    encouraging,  following,  crouching,  hiding  ; 
teaching,  etc.  imitating. 

8.  Autumn  migration  to  Migration  with  adults  or 
winter  quarters — singly,  or  independently. 

in  company  with  individuals 
of  the  same  or  of  different 
species. 

Retrospect. — In  the  lower  reaches  of  the  animal  king- 
dom there  is  prolific  multiplication  and  great  mortality ; 
or,  from  another  point  of  view,  a  life  full  of  hazards  and 
high  reproductivity  to  cope  with  these.  It  has  been  one 
of  the  great  steps  in  evolution  to  economize  life,  and  one  of 
the  most  successful  ways  of  doing  this  has  been  by  parental 
care,  of  which  affection  is  a  consequence.  As  Chalmers 
Mitchell  expresses  it :  '  The  mere  toleration  of  the  young 
by  the  mother  is  a  new  beginning  in  life,  and  is  the  foun- 
dation of  many  of  the  highest  qualities  displayed  by  the 
highest  animals  and  by  man  himself  '.  .  .  .  The  relations 
of  the  young  to  the  mother  '  are  a  continuation  of  the 
organic  relation  by  which  the  young  are  born  of  the  body 
of  their  mother,  and  they  exist  and  become,  so  to  speak, 
a  habit,  before  the  individuality,  the  physical  powers,  and 
the  senses  and  aptitudes  of  the  young  are  really  awakened '. 
.  .  .  Later  on  we  have,  of  course,  affection  as  well  as 
care ;  and  families  lead  on  to  societies. 

The  Individual  and  the  Race.— When  we  study  the 
modes  of  multiplication,  or  the  instinctive  provision  made 
for  the  young,  or  the  more  deliberate  parental  care  of  higher 
animals,  we  cannot  but  be  struck  by  the  fact  that  what  is 


THE  CYCLE   OF  LIFE  433 

done  is  often  very  far  from  advantageous  to  the  individual. 
It  is  advantageous,  indeed  essential,  for  the  species,  but 
it  is  exhausting,  sometimes  fatal,  to  the  single  life.  As 
Goethe  said,  Nature  '  cares  nothing  for  individuals '. 

Animals  do  not  indeed  foresee  that  their  reproduction 
is  going  to  be  fatal  to  them  ;  the  instinctive  mother-insect 
does  not  know  that  she  will  never  see  her  offspring  emerge 
from  the  eggs  around  which  she  places  a  store  of  laboriously 
collected  food  ;  we  have  no  reason  to  believe  that  she  has 
any  picture  of  offspring ;  when  animals  are  fatigued, 
as  their  brain-cells  show  them  to  be,  they  probably  suffer 
no  weariness,  and  they  are  doubtless  unquestioning  ;  they 
are  borne  on  by  impulses  and  instincts  which  are  as  com- 
pelling as  hunger  and  thirst.  But  the  point  is  that  these 
strong  instincts  bear  them  to  expenditures  of  energy  which 
are  not  self-preservative,  but  objectively  other-regarding. 
In  some  cases,  it  is  true,  there  is  the  reward  of  reproductive 
gratification,  and  Emerson  was,  we  believe,  profoundly 
right  when  he  suggested  that  the  imperiousness  of  sex 
desire  was  necessary  in  order  to  make  organisms  (especially 
the  higher  animals)  face  reproduction.  But  the  reward 
of  sex- gratification  only  applies  to  a  limited  set  of  cases, 
and  even  for  it  many  animals  have  to  pay  heavily.  As 
Goethe  said  :  '  She  holds  a  couple  of  draughts  from  the  cup 
of  love  to  be  fair  payment  for  the  pains  of  a  lifetime '. 
We  are  brought,  then,  to  face  the  great  fact  of  Organic 
Nature,  that  those  forms  of  life  tend  to  survive  in  which 
the  individual  has  been  more  or  less  subordinated  to  the 
welfare  of  the  species.  Metaphorically,  that  is  part  of 
Nature's  strategy.  Literally,  the  prolific  species-preserving 
types  have  survived. 

Reproduction  is  physiologically  expensive.  The  sturgeon , 

FF 


434  THE   WONDER  OF  LIFE 

whose  unlaid  eggs  form  the  delicacy  known  as  caviare, 
liberates  more  than  a  million.  There  may  be  100,000  sperma- 
tozoa in  a  cubic  millimetre.  Many  female  butterflies  die 
after  oviposition,  and  the  same  is  true  even  of  robust 
animals  like  lampreys.  The  drone  who  succeeds  in  fertilizing 
the  queen  hive-bee  dies  as  he  succeeds  ;  all  the  others,  who 
are  unsuccessful,  also  die.  A  male  spider  often  lays  his  life 
on  the  altar  of  sex,  and  the  same  is  true  of  some  scorpions. 
Viviparity  is  costly  to  the  female,  especially  in  Mammals  ; 
parturition  is  often  exhausting ;  feeding  the  young  is  a 
drain  on  the  mother's  resources. 

In  a  very  interesting  essay,  ISEspece  el  son  serviteur 
(Paris,  1913),  Professor  Cresson  has  illustrated  the  degree 
to  which  the  individual  is  subordinated  to  the  welfare  of 
the  species.  Apart  from  the  physiological  sacrifice  alluded 
to,  there  is  the  energy  expended  in  securing  the  safety  of 
the  eggs,  and  in  providing  nourishment  for  the  young. 
In  many  insects,  such  as  sand-wasps  and  scarabees,  the 
amount  of  work  done  for  the  welfare  of  the  progeny  is  very 
great.  The  non-existent  offspring  act,  Cresson  somewhat 
fancifully  suggests,  as  '  moral  parasites  '  on  their  parents. 

There  is  fatigue  in  nest-making,  risk  in  incubation, 
and  both  in  attending  to  the  nourishment,  health,  and 
education  of  the  young.  Especially  the  mothers  are,  so  to 
speak,  exploited,  Nature  taking  advantage  of  their  capacity 
for  self-forgetfulness.  Less  metaphorically,  it  is  their 
meat  and  drink  to  spend  themselves  for  the  race.  In  the 
case  of  social  insects,  the  subordination  of  the  single  life 
is  extraordinary,  sometimes  almost  pathological.  Cresson, 
indeed,  suggests  the  formula, '  Everything  for  the  species ; 
everything  by  the  individual ;  nothing  for  the  individual '. 

Ageing   and   Senescence. — In  most   animals,  as  we 


THE   CYCLE   OF  LIFE  435 

have  seen,  there  is  a  definite  limit  of  growth,  which  we 
regard  as  the  fittest  size  for  the  given  organization  and 
the  given  conditions  of  life.  Departures  from  the  norm 
have  been  persistently  pruned  off  in  the  course  of  Natural 
Selection.  Similarly  in  many  animals  there  is  a  normal 
length  of  life  (a  potential  duration  of  life)  which  is  rarely 
exceeded,  though  it  may  be  seldom  attained.  Many  of  the 
facts  in  regard  to  unusual  length  of  life  refer  to  animals 
in  captivity,  and  it  is  quite  likely  that  a  creature  may 
survive  longer  in  a  sheltered  life  than  when  it  is  subject  to 
the  struggle  for  existence.  On  the  other  hand,  the  dura- 
tion of  life  in  captivity  can  hardly  lead  us  to  over-estimate 
the  potential  duration  of  life  in  nature,  since  the  artificial 
conditions  are  bound  to  be  less  wholesome.  The  facts  in 
regard  to  captive  animals  tell  us  that  the  creatures  can 
live  to  such  and  such  an  age ;  but  this  may  be  far  above 
their  average  length  of  lif e.  It  is  very  unlikely  that  many 
wild  parrots  approach  the  century  which  is  their  potential 
longevity.  In  the  case  of  domestic  animals,  few  fowls  are 
allowed  to  survive  for  five  years,  though  they  might  live 
for  a  score ;  few  cattle  are  allowed  to  reach  the  end  of 
their  tether,  which  is  about  thirty;  and  just  the  same 
applies  to  the  average  length  of  life  in  Nature,  since  most 
wild  animals  come  to  a  violent  end. 

Dr.  Chalmers  Mitchell's  critical  revision  of  the  data 
available  in  regard  to  the  duration  of  life  in  mammals 
and  birds  goes  to  show  that  most  of  the  previous  estimates 
have  been  too  high.  Though  a  hundred  years  may  be  the 
probable  limit  for  the  elephant,  twenty  to  thirty  years  is  a 
fair  average  duration.  A  polar  bear  lived  to  thirty -three 
years  in  the  Zoo.  The  potential  longevity  of  lions  is  between 
thirty  and  forty  years  ;  that  of  some  of  the  largest  Ungu- 


436  THE  WONDER  OF  LIFE 

lates  about  fifty.  It  is  rather  interesting  that  human 
longevity  is  probably  greatest  of  all  among  mammals, 
with  the  possible  exception  of  the  large  whales. 

As  regards  birds,  more  than  one  centenarian  parrot  has 
been  recorded,  and  the  same  age  is  credited  to  some  birds 
of  prey.  A  raven  of  sixty-nine  is  authenticated,  and  an 
eagle  of  sixty-eight.  Herons,  swans,  and  geese  have  a  high 
potential  longevity,  and  an  ostrich  is  said  to  be  capable  of 
occasionally  surviving  for  a  term  of  thirty-five  years. 
A  giant  tortoise  (Testudo  gigantea)  that  was  living  near 
Colombo  in  1796,  when  Ceylon  was  first  occupied  by  the 
British,  survived  until  1894,  so  that  it  must  have  been  more 
than  a  centenarian. 

In  the  case  of  Man,  we  must  clearly  distinguish  between 
the  average  specific  longevity,  about  thirty-four  years  in 
Europe — but  happily  raisable  with  decreasing  infantile 
mortality,  improved  sanitation,  decreasing  warfare,  increas- 
ing temperance  and  carefulness — and  the  potential  specific 
longevity,  which  for  the  present  race  is  normally  between 
seventy  and  one  hundred  years.  There  is  no  warrant  for  fix- 
ing an  ultimate  limit,  either  for  the  past  or  the  future.  All 
that  we  can  scientifically  say,  is  that  there  are  few  well- 
established  instances  of  a  greater  human  longevity  than 
104  years.  Sir  George  Cornewall  Lewis  did  good  service 
(1862)  in  destructively  criticizing  numerous  alleged  cases  of 
centenarianism,  the  occurrence  of  which  he  at  first  regarded 
as  quite  unproved,  but  even  he  finally  admitted  that  men 
do  sometimes  reach  a  hundred  years,  and  that  some  have 
reached  one  hundred  and  three  or  four.  The  famous 
cases  of  Thomas  Parr,  Henry  Jenkins,  and  the  Countess 
of  Desmond,  said  to  be  152,  169,  and  140  respectively,  were 
ruled  out  of  court  by  Mr.  Thorns,  who  edited  Notes  and 


THE   CYCLE   OF  LIFE  437 

Queries  at  the  time  when  Sir  G.  C.  Lewis's  wholesome 
scepticism  created  much  stir.  As  man  is  a  slowly  varying 
organism,  as  regards  physical  characters  at  least,  it  is 
extremely  unlikely  that  his  longevity  was  ever  much  greater 
than  it  is  now.  Monsters  in  age  and  monsters  in  size  are 
alike  incredible. 

A  fact  of  much  interest  is  the  statistical  evidence 
that  such  a  subtle  character  as  '  longevity ',  that  is  to 
say,  a  tendency  to  a  certain  lease  of  life,  be  it  long  or  short, 
is  heritable  like  other  inborn  characters,  though  it  rests 
of  course  to  some  extent  with  the  individual  or  his  environ- 
ment to  determine  whether  the  inherited  tendency  is 
realized  or  not.  Just  as  stature  is  a  heritable  quality,  so  is 
potential  longevity,  but  the  degree  of  expression  is  in  part 
determined  by  '  nurture '  in  the  widest  sense. 

Professor  E.  MetchnikofE  is  one  of  the  few  modern  biolo- 
gists who  would  deal  generously  with  biblical  and  other  old 
records  of  great  human  longevity.  He  apparently  thinks 
there  has  been  some  misunderstanding  in  regard  to  Methu- 
saleh's  969  years  or  Noah's  595,  but  he  accepts  the  great 
ages  of  175,  180,  and  147  years  ascribed  to  Abraham,  Isaac, 
and  Jacob.  Similarly,  he  accepts  the  185  years  with  which 
St.  Mungo  of  Glasgow  has  been  credited.  And  as  he  is 
generous  in  regard  to  the  past,  he  is  hopeful  in  regard  to  the 
future,  believing  that  a  more  careful  and  temperate  life, 
as  well  as  an  enlightened  recognition  of  the  disharmonies  of 
our  bodily  frame,  may  bring  about  a  time  when  man  will 
no  longer,  as  Buffon  said,  die  of  disappointment,  but 
attain  everywhere  a  hundred  years.  '  Humanity ', 
Metchnikoff  says,  '  would  make  a  great  stride  towards 
longevity  could  it  put  an  end  to  syphilis,  which  is  the  cause 
of  one-fifth  of  the  cases  of  arterial  sclerosis.  The  sup- 


438  THE  WONDER  OF  LIFE 

pression  of  alcoholism,  the  second  great  factor  in  the  pro- 
duction of  senile  degeneration  of  the  arteries,  will  produce 
a  still  more  marked  extension  of  the  term  of  life.  Scien- 
tific study  of  old  age  and  of  the  means  of  modifying  its 
pathological  character  will  make  life  longer  and  happier '. 
He  also  quotes  the  theoretically  simple  conclusion  of  Pfliiger 's 
essay  on  The  Art  of  Prolonging  Human  Life — '  Avoid  the 
things  that  are  haimful  and  be  moderate  in  all  things '. 
Attempts  have  often  been  made  to  correlate  the  duration 
of  an  animal's  life  with  its  structural  or  functional  character- 
istics, and  up  to  a  certain  point  this  way  of  looking  at  it  is 
useful.  For  the  living  creature  is  a  consistent  unity,  and 
its  length  of  life  must  be  correlated  with  its  whole  being. 
It  is  evident  that  a  very  large  animal  will  not  be  a  very 
short-lived  animal,  but  the  difficulty  is  that  animals  equal 
in  size  are  often  very  far  from  equal  in  length  of  life.  It  is 
natural  that  a  relatively  easy-going  animal  like  a  sea-anemone 
should  be  able  to  survive  very  much  longer  than  an  intensely 
living  insect,  but  the  difficulty  is  that  equally  active  insects 
may  differ  greatly  in  their  length  of  life.  In  his  famous 
essay  On  the  Duration  of  Life  (1881)  Weismann  considered 
the  various  attempts  to  correlate  length  of  life  with  size, 
with  intensity  of  life,  with  the  duration  of  the  growing 
period,  and  so  on,  but  found  that  none  of  the  correlations 
could  be  generalized.  He  was  led  to  the  conclusion  that 
length  of  life,  like  size,  is  an  adaptive  character  gradually 
defined  in  relation  to  the  conditions  of  life  of  the  species. 
If  a  species  is  endangered  in  the  struggle  for  existence, 
and  shows  a  decline  of  population — too  high  a  death-rate 
in  proportion  to  its  birth-rate — then,  seeing  that  length 
of  life  is  a  very  variable  quality,  the  species  may  be  saved 
by  the  Natural  Selection  of  the  longer-lived  variants,  who 


THE  CYCLE  OF  LIFE  439 

in  virtue  of  some  constitutional  toughness  survive  longer 
and  have  more  offspring.  As  Dr.  Chalmers  Mitchell 
points  out,  however,  the  process  might  work  the  other 
way  round  by  a  selection  of  those  variants  showing 
increased  reproductivity.  If  the  specific  duration  of  life 
happened  to  be  a  very  fixed  character,  and  the  fertility 
very  variable,  the  line  of  solution  might  be  as  Dr.  Chalmers 
Mitchell  indicates.  Both  theories  may  be  right.  Unfortun- 
ately, neither  admits  of  verification  as  regards  the  past. 

Death. — In  spite  of  criticisms,  we  find  no  good  reason 
against  accepting  Weismann's  doctrine  of  the  immor- 
tality of  the  Protozoa.  Truly,  these  simple  organisms 
do  not  live  a  charmed  life ;  they  are  continually  being 
killed  in  countless  millions  ;  they  are  sometimes  consumed 
by  parasites,  and  so  on  ;  but  the  point  is  that  some  of 
them  at  least  are  not  subject  to  natural  death  in  the  same 
degree  as  higher  animals  are  ;  that  some  of  them,  indeed, 
may  be  exempt  from  natural  death  altogether.  To  be 
devoured  by  other  creatures,  to  be  dried  up  by  the  sun, 
to  be  killed  by  a  sudden  change  of  temperature,  that  is  the 
fate  of  many ;  but  that  is  violent  death.  Others  are 
occasionally  destroyed  by  internal  parasites  smaller  and 
simpler  than  themselves,  but  that  is  microbic  death.  To 
the  natural  death  which  ensues  from  the  physiological 
insolvency  of  the  body  they  are  immune.  The  reasons 
are  to  be  found  in  their  relative  simplicity  of  structure ; 
they  can  continuously  make  good  their  wear  and  tear ; 
and  in  their  relatively  simple  modes  of  multiplication, 
which  do  not  involve  the  nemesis  so  familiar  in  higher 
animals.  It  is  well  known  that  a  family  of  Infusorians  all 
descended  from  one  individual  isolated  in  a  basin  will  often 
come  to  an  end,  one  of  the  reasons  being  the  absence  of 


440  THE  WONDER  OF  LIFE 

any  conjugation  or  primitive  pairing  ;  another  reason  being 
that  the  medium  is  or  becomes  in  some  way  abnormal. 
But  Weismann's  doctrine  postulates  natural  conditions, 
which  would,  of  course,  include  the  possibility  of  conjuga- 
tion, and  an  ever  fresh  medium.  A  recent  worker,  Mr. 
G.  T.  Baitsell,  reports  that  he  has  discovered  an  optimum 
medium  in  which  one  of  the  Infusorians  will  thrive  and 
multiply  indefinitely  without  conjugation  and  without 
introduced  tonics. 

It  is  a  familiar  fact  that  in  the  history  of  a  hay  infusion, 
one  kind  of  Protozoon  succeeds  another,  which  disappears 
before  it.  But  this  disappearance  is  sometimes  due  to 
violent  death,  and  is  sometimes  not  more  than  passing  into 
a  latent  state,  as  the  result  of  deficient  food  or  accumulated 
waste-products.  And  again,  it  may  be  admitted  that 
when  a  Protozoon  divides  into  two  or  many  individuals,  there 
is,  in  a  sense,  a  disappearance  of  a  particular  individuality 
which  went  through  a  particular  sequence  of  experiences  ; 
yet  we  cannot  speak  of  death  when  one  creature  directly 
turns  into  two  or  into  many,  and  when  there  is  nothing 
left  to  bury. 

It  is  not  improbable  that  very  simple  multicellular 
animals,  such  as  the  freshwater  Hydra,  may  go  on  living 
indefinitely  if  the  natural  conditions  are  altogether  pro- 
pitious. The  structure  and  the  multiplication  of  Hydra 
are  alike  so  simple,  that  there  seems  no  good  reason  why 
it  should  die  a  natural  death.  But  as  the  body  became 
more  complex,  death  was  instituted  as  a  tax  on  progress. 
In  discussing  senescence  we  have  mentioned  some  of  the 
facts  which  more  or  less  certainly  involve  natural  death, 
but  they  are  mostly  reducible  to  two  :  (1 )  That  the  effects  of 
wear  and  tear  in  the  body  are  not  readily  made  good  with 


THE  CYCLE  OF  LIFE  441 

anything  like  thoroughness,  and  (2)  that  the  process  of 
reproduction  tends  to  become  physiologically  exhausting, 
especially  to  the  female  sex.  It  is  a  noteworthy  fact, 
however,  that  in  wild  nature,  the  usual  termination  of  life 
is  violent.  Most  animals  die  before  their  time,  devoured 
by  their  fellows,  killed  off  by  some  environmental  vicissi- 
tude, or  starved  by  a  seasonal  disappearance  of  their  food. 
Very  few  cases  of  microbic  death  are  known  among  wild 
animals,  and  it  is  possible  that  all  such  cases  are  due  to 
some  human  interference.  Sir  Ray  Lankester  cites  the 
case  of  a  sandhopper  which  suffers  from  a  bacterial 
epidemic,  but  admits  that  this  may  be  quite  '  unnatural '. 
In  regard  to  the  legions  of  parasites  with  which  animals 
are  infested,  it  has  to  be  recognized  that  these  are  rarely 
fatal.  It  would  be  almost  a  contradiction  in  terms  that 
they  should  be,  for  it  is  not  advantageous  to  a  parasite 
to  kill  its  host.  Parasites  are  destructive  when  they  are 
transported  into  hosts  which  are  not  physiologically  accus- 
tomed to  them,  which  have  altered  their  geographical 
distribution,  and  thus  become  susceptible  to  novel  intruders. 
Then  we  hear  of  plagues  and  decimation,  but  in  most  cases 
parasitism  is  an  old-established,  going  concern.  There 
rise  in  the  mind  cases  like  those  of  Ichneumon-flies,  which 
lay  their  eggs  in  caterpillars  and  the  like,  and  there  the 
fatality  is  well  known.  The  Ichneumon-grubs  hatched 
in  the  caterpillar,  proceed  to  devour  their  temporary  host. 
But  this  is  not  an  ordinary  type  of  parasitism. 

On  the  whole,  therefore,  we  are  led  to  agree  with  the 
general  conclusion,  which  many  naturalists  have  reached, 
that  in  a  state  of  Nature,  most  animals  die  a  violent  death 
before  they  have  nearly  reached  the  end  of  their  tether. 
And  this  is  one  of  the  reasons  why  life  in  Nature  is  so 


442  THE  WONDER  OF  LIFE 

vigorous  and  wholesome.  As  Goethe  said,  '  Death  is  her 
expert  device  to  get  plenty  of  life.' 

Summary. — There  is,  as  we  have  hinted,  reason  to 
believe  that  natural  death  is  not  to  be  regarded  simply  as 
an  intrinsic  necessity — the  fate  of  all  life ;  we  can  carry 
the  analysis  further,  and  say  that  it  is  incident  on  the  com- 
plexity of  the  bodily  machinery,  which  makes  complete 
recuperation  wellnigh  impossible,  and  almost  forces  the 
organism  to  accumulate  arrears,  to  go  into  debt  to  itself ; 
that  it  is  incident  on  the  limits  which  are  set  to  the  multi- 
plication and  renewal  of  cells  within  the  body,  thus  nerve- 
cells  in  higher  animals  cannot  be  added  to  after  an  early 
stage  in  development ;  that  it  is  incident  on  the  occurrence 
of  organically  expensive  modes  of  reproduction,  for  repro- 
duction is  often  the  beginning  of  death.  At  the  same  time, 
it  seems  difficult  to  rest  satisfied  with  these  and  other 
physiological  reasons,  and  we  fall  back  on  the  selectionist 
view  that  the  duration  of  life  has  been,  in  part  at  least, 
punctuated  from  without  and  in  reference  to  large  issues  ; 
it  has  been  gradually  regulated  in  adaptation  to  the  welfare 
of  the  species. 

As  we  have  suggested  in  The  Biology  of  the  Seasons, 
several  groups  should  be  distinguished.  (1 )  The  first  is  that 
of  the  immortal  unicellular  animals  which  never  grow  old, 
which  seem  exempt  from  natural  death.  (2)  The  second 
is  that  of  many  animals  which  reach  the  length  of  their 
life's  tether  without  any  hint  of  ageing  and  pass  off  the 
scene — or  are  shoved  off — victims  of  violent  death.  In 
many  fishes  and  reptiles,  for  instance,  which  are  old  in  years, 
there  is  not  in  their  organs  or  tissues  the  least  hint  of  age- 
degeneration.  (3)  The  third  is  that  of  the  majority  of 
civilized  human  beings,  some  domesticated  and  some  wild 


THE  CYCLE   OF  LIFE  443 

animals,  in  which  the  decline  of  life  is  marked  by  normal 
senescence.  (4)  The  fourth  is  that  of  many  human  beings, 
not  a  few  domesticated  animals,  e.g.  horse,  dog,  cat,  and 
some  semi-domesticated  animals,  notably  bees,  in  which 
the  close  of  life  is  marked  by  distinctively  pathological 
senility.  It  seems  certain  that  wild  animals  rarely  exhibit 
more  than  a  slight  senescence,  while  man  often  exhibits 
a  bathos  of  senility.  What  is  the  reason  of  this  ? 

The  majority  of  wild  animals  seem  to  die  a  violent  death, 
before  there  is  time  for  senescence,  much  less  senility. 
The  character  of  old  age  depends  upon  the  nature  of  the 
physiological  bad  debts,  some  of  which  are  more  unnatural 
than  others,  much  more  unnatural  in  tamed  than  in  wild 
animals,  much  more  unnatural  in  man  than  in  animals. 
Furthermore,  civilized  Man,  sheltered  from  the  extreme 
physical  forms  of  the  struggle  for  existence,  can  live  for  a 
long  time  with  a  very  defective  hereditary  constitution, 
which  may  end  in  a  period  of  very  undesirable  senility. 
Man  is  very  deficient  in  the  resting  instinct,  and  seldom 
takes  much  thought  about  resting  habits.  In  many  cases, 
too,  there  has  come  about  in  human  societies  a  system  of 
protective  agencies  which  allow  the  weak  to  survive  through 
a  period  of  prolonged  senility.  We  cannot,  perhaps,  do 
otherwise  ;  but  it  is  plain  that  to  heighten  the  standard 
of  vitality  is  an  ideal  more  justifiable  biologically  than 
that  of  merely  prolonging  existence.  For  if  old  age  be 
then  permitted,  it  is  more  likely  to  be  without  senility. 
Those  whom  the  gods  love  die  young. 

IN  ILLUSTRATION 

Freshwater  Sponge. — Some  of  the  simplest  animals 
or  Protozoa  have  very  complex  life-histories,  especially 


444  THE  WONDER  OF  LIFE 

in  some  of  the  parasitic  forms  ;  but  they  are  too  difficult 
for  discussion  here.  As  a  first  illustration,  therefore,  we 
take  a  multicellular  animal,  the  freshwater  sponge.  In 
some  of  the  freshwater  sponges — which  form  the  family 
Spongillidse,  aberrant  in  having  left  the  sea — an  interesting 
alternation  of  generations  has  been  described  by  W.  Mar- 
shall and  others.  In  autumn  the  sponge,  which  grows 
on  sticks  and  stones  in  the  river  or  lake,  suffers  from  the 
cold  and  from  a  scarcity  of  food.  It  begins  to  die. 
Throughout  the  moribund  body,  however,  little  companies 
of  cells  group  themselves  together  and  become  surrounded 
by  a  protective  capsule  of  tightly -fitting,  somewhat  capstan- 
like,  flinty  spicules.  Each  group  is  called  a  gemmule, 
and  while  the  parent  dies,  the  gemmules  survive  the  winter. 
In  April  or  May  they  float  away  from  the  debris  of  the  old 
body,  and  develop  into  new  sponges.  Some  become  short- 
lived males,  others  more  stable  females.  The  ova  produced 
by  the  latter  and  fertilized  by  spermatozoa  from  the  former, 
develop  into  a  summer  generation  of  asexual  sponges, 
which,  in  turn,  die  away  in  autumn,  and  give  rise  to  gem- 
mules.  The  formation  of  gemmules  is  an  asexual  mode 
of  multiplication,  and  it  also  secures  dispersal,  for  the  gem- 
mules  can  be  swept  about  by  currents  without  being 
damaged,  until  eventually  they  effect  lodgment  in  some 
crevice  and  begin  to  develop. 

Zoophytes  and  Swimming  Bells. — Many  of  the 
graceful  colonies  of  Hydroid  polyps,  often  called  Zoophytes, 
liberate  in  the  summer  months  transparent  reproductive 
buds  specialized  for  free-swimming.  These  Medusoids, 
which  are  in  a  very  general  way  like  miniature  jelly-fishes 
or  Medusae,  swim  in  the  open  water  by  contractions  and 
expansions  of  their  bells.  They  are  sexual  stages  in  the 


FIG.  68.— Life  History  of  a  Hydrozoon,  Bougainvillia  fruticosa.  A.  The  zoophyte 
colony,  natural  size.  B.  A  portion  enlarged,  showing  PE  ,  protective  perisarc  • 
L.  1  he  hvmg  connexion  between  the  polyps  ;  NP.  a  nutritive  polyp,  MB.  a  medu- 
soid bud,  M.  a  medusoid  about  to  be  liberated.  C.  A  free-swimming  sexual 
medusoid.  (After  Allman.) 


THE  CYCLE  OF  LIFE  445 

life-history,  and  produce  ova  and  spermatozoa.  The 
fertilized  ova  develop  into  free-swimming  embryos,  which 
soon  settle  down  and  become  polyps.  Each  polyp  is  the 
beginning  of  a  hydroid  colony  which  is  formed  by  repeated 
budding.  Thus  there  is  a  remarkable  alternation  between 
a  fixed,  plant-like,  vegetative,  asexual  hydroid  colony  or 
zoophyte,  and  a  free,  active,  sexual  medusoid  or  swimming 
bell.  A  similar  separation  of  the  life-history  into  two  very 
markedly  contrasted  chapters  is  common  among  Ccelentera 
or  Stinging  Animals  ;  we  find  it  again  in  many  Trematodes 
like  the  liver-fluke ;  in  some  insects,  like  the  gall- wasps  ; 
and  in  remarkable  expression  in  the  free-swimming  Tuni- 
cates  known  as  Salps.  It  is  also  characteristic  of  ferns 
and  mosses  and  the  like,  and  it  occurs  in  disguised  form 
in  flowering  plants.  It  may  be  defined  as  the  alternate 
occurrence  in  one  life-history  of  two  or  more  different 
forms  differently  produced. 

The  Common  Jelly-fish. — Every  one  who  knows  the 
sea  at  all  is  familiar  with  swimming  or  drifting  shoals 
of  the  common  jelly-fish,  Aurelia  aurita,  one  of  the  most 
cosmopolitan  of  animals.  The  glassy  disc,  with  a  shimmer 
of  light  violet,  is  usually  about  four  inches  in  diameter ; 
it  is  surrounded  by  minute  circumference  tentacles,  and 
eight  sense-organs  symmetrically  arranged  in  niches  ;  four 
frilled  lips  hang  down  from  the  central  mouth  on  the  under 
side  ;  eight  branched  and  eight  unbranched  canals  radiate 
out  from  the  central  stomach  to  a  peripheral  canal ;  and 
there  are  four  conspicuously  coloured  male  or  female 
reproductive  organs.  The  fertilized  eggs  develop  into 
minute  free-swimming  oval  larvae,  which  after  a  short 
period  of  activity  settle  down  on  a  stone  or  seaweed. 
They  develop  into  little  polyp-like  forms,  known  as  '  Hydra 


446 


THE  WONDER  OF  LIFE 


FIG.  69. — Minute  trans- 
parent free-swimming 
larva  of  a  sea-cucum- 
ber or  Holothurian, 
showing  transverse 
bands  of  cilia  (c) 
and  peculiar  protrud- 
ing '  arms '  (A). 


tubae,'  about  an  eighth  of  an  inch  in  height,  with  a  mouth, 
gullet,  and  tentacles.  In  ordinary  conditions  this  sedentary 
stage  grows  larger,  and  displays  a 
series  of  transverse  annular  con- 
strictions, becoming  like  a  minia- 
ture pile  of  saucers — the  strobila 
stage.  Each  disc  or  saucer  is 
separated  off  in  turn  as  a  free- 
swimming  young  jelly-fish  (or 
Ephyra),  which  feeds  on  micro- 
scopic organisms,  grows  rapidly, 
undergoes  certain  structural 
changes,  and  becomes  a  sexual 
jelly-fish.  Thus  we  find  that  a 
characteristically  free  and  active 
animal,  the  jelly-fish,  includes  in  its  life-history  a  fixed 
and  vegetative  polyp-stage — alternation  of  generations 
again  (see  Fig.  72). 

Echinoderms.  —  The  newly- 
hatched  larvae  of  sea-urchins,  sea- 
cucumbers,  starfishes,  and  brittle 
stars  are  diffusely  ciliated  two- 
layered  thimble-like  sacs — in  fact, 
not  very  remarkable  gastrulae. 
But  they  soon  become  quaintly 
transformed  by  the  outgrowth  of 
processes  and  the  formation  of 
special  bands  of  cilia  into  extra- 
ordinarily shaped  larvae,  adapted 
for  open  sea  life.  In  sea-urchins, 
for  instance,  the  quaint  larva, 
known  as  a  Pluteus,  is  often 


FIG.  70.  —  Minute  trans- 
parent free-swimming 
larva  of  a  sea-cucum- 
ber or  Holothurian, 
showing  peculiar  pro- 
truding '  arms '  (A) 
and  calcareous  plates 
(CP). 


THE  CYCLE  OF  LIFE  447 

compared  to  a  microscopic  six-legged  easel,  and  the 
same  type  occurs  in  Brittle-stars.  Those  of  starfishes 
and  sea-cucumbers  baffle  brief  description.  Those  of 
feather-stars  or  Crinoids  are  not  so  divergent. 

But  even  more  remarkable  than  the  shape  of  the  larvae 
is  the  fact  that  they  do  not  develop  directly  into  the  adult, 
in  the  way  in  which  a  tadpole  develops  into  a  frog.  The 
development  is  circuitous.  Within  the  larva  a  new  forma- 
tion begins,  on  a  fresh  architectural  plan,  utilizing  some 
parts  and  rejecting  others,  and  the  result  is  the  adult 
form  (Fig.  21).  The  curious  arms  or  processes  characteristic 
of  the  larva  are  in  part  absorbed  and  in  part  thrown  off. 
The  wandering  amoeboid  cells  which  play  so  diverse  and 
important  a  role  in  the  animal  kingdom  are  very  active, 
at  once  as  sappers  and  miners  in  breaking  down,  and  as 
builders  in  the  re-construction. 

Mermis  and  Horse -hair  Worms. — A  curious  sight  is 
sometimes  seen  in  gardens,  especially  after  heavy  rains 
in  summer — a  thin  thread  of  a  worm  raising  itself  into  the 
air  from  the  top  of  a  cabbage  plant  and  writhing  as  if  in 
search  of  something.  That  is  a  female  Mermis,  and  it  is 
supposed  to  be  seeking  out  a  place  for  egg-laying  more 
suitable  than  the  very  damp  earth.  This  is  an  episode  in  a 
curious  life-history.  The  mature  Mermithidse  live  in  the 
earth  or  in  fresh  water,  and  so  do  the  first  larval  stages. 
From  the  earth  or  water,  the  young  larvae  migrate  and 
bore  actively  into  beetles,  caterpillars,  millipedes,  slugs, 
and  so  on.  When  they  become  mature,  the  worms  leave 
their  hosts.  Now  it  is  noteworthy  that  no  food  is  taken 
either  by  the  adults  or  by  the  young  larvae.  All  the 
feeding  is  done  by  the  second  larval  forms  during  the 
parasitic  period.  Many  adult  insects  are  non-nutritive 


448  THE  WONDER  OF  LIFE 

and  wholly  reproductive,  using  the  energy  accumulated 
in  the  larval  period ;  but  in  the  Meimithidse  the  state  of 
affairs  is  even  more  striking,  for  the  energy  accumulated 
in  the  second  larval  stage  serves  not  only  for  mature  life 
and  for  reproduction,  but  also  for  the  first  chapter  in  the 
life  of  the  next  generation  !  The  black  horse-hair  worms, 
hundreds  of  which  are  sometimes  seen  in  a  little  wayside 
pool,  each  about  the  thickness  of  a  hair  from  a  horse's  tail, 
have  a  somewhat  similar  life-history.  The  minute  larvae 
enter  water-beetles  and  other  insects  and  grow  large  within 
them,  to  a  length  of  four  inches  or  so,  much  longer  indeed 
than  their  hosts.  When  they  become  mature  they  work 
their  way  out  of  the  insects  and  sometimes  suddenly  appear 
in  large  numbers  in  the  pools.  We  have  seen  a  pool  a 
couple  of  feet  across,  so  crowded  with  them  that  over  a 
hundred  could  be  lifted  in  a  handful,  just  like  a  bunch  of 
vitalized  hairs,  as  the  mediaeval  naturalists  believed  them 
to  be. 

Barnacles  and  Acorn-Shells. — The  barnacles  (Lepas, 
etc.)  on  floating  timber  and  the  acorn-shells  (Balanus) 
encrusting  the  shore  rocks  are  much  alike  in  their  life- 
history,  and  a  very  remarkable  one  it  is.  Out  of  the  egg 
of  the  barnacle  there  emerges  a  minute  free-swimming 
larva — a  Nauplius — with  three  pairs  of  appendages,  an 
unpaired  eye  and  a  delicate  dorsal  shield.  After  moulting 
several  times,  it  fixes  itself  by  means  of  its  first  pair  of 
feelers,  which  have  become  suctorial,  to  some  floating 
object,  and  secures  its  adhesion  by  a  secretion  of  gluey 
material.  The  anterior  end  by  which  it  has  fixed  itself 
is  drawn  out  into  a  long  flexible  stalk,  and  a  thorough- 
going change  occurs  in  the  bodily  structure,  until  the  final 
form  is  reached.  During  this  metamorphosis  the  animal 


THE  CYCLE  OF  LIFE 


449 


fasts,  living  on  its  stores.  Out  of  the  egg  of  the  Balanus 
a  nauplius  larva  likewise  emerges.  It  feeds  and  grows 
and  moults,  and  acquires  a  firmer  dorsal  shield,  a  longer 


FIG.  71. — I.  An  acorn-shell  (Balanus),  showing  :  1,  the  external  rampart 
of  calcareous  plates ;  2,  the  valves  which  shut  in  over  the  retracted 
body;  3,  some  of  the  thoracic  appendages  protruded.  II. 
The  free-swimming  larva  of  the  same,  known  as  a  nauplius  :  1,2,3, 
first  three  pairs  of  limbs,  corresponding  to  the  antennules,  antennae, 
and  mandibles  of  the  adult.  It  is  almost  microscopic. 


spined  tail,  and  stronger  appendages.  It  then  changes 
into  a  somewhat  *  water-flea  '-like  form — the  Cyprid 
stage — with  two  lateral  eyes,  six  pairs  of  swimming  append- 
ages, a  bivalve  shell,  and  so  on.  It  is  very  active,  but  it 

GG 


450 


THE  WONDER  OF  LIFE 


does  not  feed,  so  that  not  unnaturally  it  soon  comes  to 
rest  as  if  in  fatigue.  It  fixes  itself  head  downwards  on  the 
rock  or  shell  by  means  of  its  first  pair  of  feelers  and  some 
glutinous  cement.  It  loses  its  bivalve  shell  and  makes 


Fia.  72. — Life-history  of  the  common  jelly-fish,  Aurelia  aurita.  (After 
Bronn.)  1,  the  free-swimming  ciliated  planula  ;  2,  the  same  fixed  ; 
3,  the  hydra-tuba,  with  four  tentacles  ;  4  and  5,  the  strobila  or  pile-of- 
saucers  stage ;  6,  a  later  stage  after  most  of  the  discs  have  been 
separated  off ;  7,  a  separated  off  disc  or  ephyra,  showing  8  bifid 
processes  each  with  a  sense-organ  ;  8-9,  the  ephyra  seen  from  the 
side  and  from  beneath.  The  mouth  is  shown  in  the  centre. 


THE  CYCLE  OF  LIFE  451 

another  of  a  different  pattern  ;  it  undergoes  a  metamor- 
phosis, fasting  all  the  time,  and  becomes  a  miniature 
adult  with  its  beautifully  waving  curl-like  appendages — 
comparable,  as  Huxley  said,  to  a  shrimp  fixed  head  down- 
wards and  back  downwards  to  a  rock,  and  kicking  its 
food  into  its  mouth  with  its  legs. 

Shore  Crab. — No  one  could  suspect  from  an  obser- 
vation of  a  common  shore-crab,  such  as  Carcinus  mcenas, 
that  its  early  youth  was  spent  in  open  waters.  The  larva 
is  a  minute  transparent  free-swimming  creature,  known 
as  a  zosea,  with  its  tail  sticking  out  in  a  line  with  the  rest 
of  the  body,  with  eight  pairs  of  limbs  instead  of  the  adult's 
total  of  at  least  twice  as  many,  and  with  a  curved  spine 
arising  from  the  middle  of  the  cephalothorax  shield.  This 
little  animal  feeds  and  grows  and  moults  its  cuticle,  and 
feeds  and  grows  and  moults  again,  becoming  eventually 
a  second  larval  form,  known  as  the  Megalops.  This  has 
lost  the  spine  and  gained  a  broader  body  and  also  additional 
limbs,  namely  those  corresponding  to  the  forceps  and 
walking  legs  of  the  adult  crab.  But  its  tail  is  still  sticking 
out  in  a  line  with  the  rest  of  the  body.  The  Megalops  feeds 
and  grows  and  moults,  gets  its  tail  tucked  forwards  under 
the  cephalothorax,  and  becomes  a  miniature  crab  about 
the  size  of  a  quarter  of  one's  little  finger  nail — a  creature  no 
longer  suited  for  free  swimming,  but  for  the  floor  of  the 
sea  in  shallow  water,  whence  it  creeps  up  on  to  the 
shore. 

Freshwater  Insects. — There  is  something  peculiarly 
fascinating  in  the  life-histories  of  freshwater  insects,  partly 
because  of  the  sharp  contrast  between  the  aquatic  and 
the  aerial  chapters,  partly  because  of  the  subtlety  of  the 
adaptations  to  life  in  the  water.  Every  one  has  enjoyed 


452  THE  WONDER  OF  LIFE 

Tennyson's  picture,  which  is  only  one  out  of  a  possible 
score  equally  dramatic. 

To-day  I  saw  the  dragon-fly 

Come  from  the  wells  where  he  did  lie. 

An  inner  impulse  rent  the  veil 

Of  his  old  husk :    from  head  to  tail 

Came  out  clear  plates  of  sapphire  mail. 

He  dried  his  wings;    like  gauze  they  grew; 

Thro'  crofts  and  pastures  wet  with  dew 

A  living  flash  of  light  he  flew. 

May -Flies. — Not  unfamiliar  in  May  or  June  is  the  emer- 
gence of  a  crowd  of  May-Flies  or  Ephemerides  from  the 
pond  or  from  a  backwater  of  the  river.  In  our  Biology 
of  the  Seasons  we  have  described  the  long  larval  life  in 
the  water,  sometimes  lasting  for  two  or  three  years ;  the 
growth  and  the  moultings  ;  the  final  moult,  the  unfolding 
of  the  filmy  wings,  and  the  transient  aerial  dance  some- 
times lasting  only  for  a  day.  The  long-drawn-out  nutritive 
and  growing  period  stands  in  remarkable  contrast  to  the 
hurried  reproductive  chapter.  They  rise  like  a  living 
mist  from  the  pond ;  they  dance  in  the  pleasant  light  of 
the  summer  evening ;  they  dimple  the  smooth  water  into 
smiling  with  a  touch,  chasing,  embracing,  separating.  .  .  . 
'  They  never  pause  to  eat — they  could  not  an  they  would  ; 
hunger  is  past,  love  is  present,  and  in  the  near  future  is 
death.  The  evening  shadows  grow  longer — shadows  of 
death  to  the  day-flies.  The  trout  jump  at  them,  a  few 
rain-drops  help  to  thin  the  throng,  the  stream  bears  others 
away.  The  mothers  lay  their  eggs  in  the  water  and  wearily 
die  forthwith,  cradle  and  tomb  are  side  by  side ;  and  the 
males  also  pass  from  the  climax  of  love  to  the  other  crisis 
of  dying.  But  after  all,  the  eggs  are  in  the  water,  the 


THE  CYCLE  OF  LIFE 


453 


promise  of  the  future ;    the  individuals  perish,  but  the 
race  lives  on.' 

Gnats. — Early  in  spring  we  may  find  the  gnats'  boat 
of  300  eggs  moored  to  the  water-weed.  Early  in  May 
the  larvse  abound  in  the  pools,  quaint,  dark-coloured 
creatures,  about  half  an  inch  long,  with  slender  biistly 
bodies,  and  mouth-parts  which  waft  in  food-particles. 


FIG.  73. — I,  Larva.  II.  Pupa  of  the  Gnat  (Culex  pipiens).     (After  Hurst.) 
BT,  respiratory  tubes.     T,  tail  end  of  larva. 

They  seem  to  spend  their  day  between  the  bottom  of  the 
pool  and  the  surface-film,  which  they  perforate  with  a 
terminal  valved  breathing  organ  at  the  end  of  the  tail. 
Hanging  head  downwards,  they  accumulate  air  enough 
to  serve  during  prolonged  submergence.  They  grow  apace 
and  moult  three  times  without  changing  much  in  their 
character.  But  at  the  fourth  moult  a  pupa  emerges,  light- 


454  THE  WONDER  OF  LIFE 

brown  in  colour,  with  a  large  head  and  a  small  body,  with 
anterior  breathing  tubes,  and  no  open  mouth.  After  a 
few  days  the  pupa  husk  splits  and  the  winged  gnat  escapes. 
Other  Insects. — No  life-history  is  more  marvellous 
than  that  of  a  moth  or  butterfly.  Out  of  the  egg,  after  a 
very  remarkable  development,  there  emerges  a  minute 
worm-like  caterpillar,  usually  active,  voracious,  and  of 
rapid  growth.  Typically,  it  shows  a  hard  head  with  biting 
mouth-parts,  with  very  minute  antennae,  and  with  several 
pairs  of  simple  eyes — in  every  respect  as  different  as  possible 
from  the  full-grown  insect's  head.  The  body  consists  of 
thirteen  or  so  segments,  of  which  the  first  three  bear  jointed 
clawed  legs,  corresponding  to,  though  they  do  not  become, 
the  three  pairs  of  thoracic  legs  in  the  adult.  Posteriorly 
there  are  four  or  five  pairs  of  unjointed,  unclawed,  leg-like 
structures — the  so-called  '  pro-legs  ' — which  are  not  repre- 
sented in  the  winged  insect.  As  it  eats  it  grows,  and 
growth  involves  moulting — the  thoroughgoing  casting  of 
the  cuticle.  There  may  be  five  of  these  moults,  each  marked 
by  respiratory  and  other  difficulties,  and  followed  by  rapid 
growth.  Finally,  having  reached  its  limit  of  growth, 
the  caterpillar  becomes  quiescent ;  it  often  surrounds  itself 
with  a  cocoon,  sometimes  silken,  and  passes  into  the 
chrysalis  or  pupa  state.  Serious  respiratory  and  other 
difficulties  beset  the  pupa ;  a  process  analogous  to  inflam- 
mation pervades  it ;  the  old  structure  is  broken  down  and 
groups  of  formative  cells  of  an  embryonic  character  proceed 
to  build  up  the  adult  body  on  a  new  architectural  plan. 
Everything  is  changed — mouth-parts,  antennae,  food-canal, 
muscles,  everything.  New  structures,  such  as  wings  and 
compound  eyes,  make  their  appearance.  By  and  by  there 
struggles  painfully  out  of  the  imprisoning  husk  an 


FIG.  74.— Life  History  of  Death's  Head  Moth  (Acherontia  atropos). 
From  a  specimen.  I.  The  caterpillar.  II.  The  pupa.  III. 
The  pupa  with  the  moth  emerging.  IV.  The  moth  at  rest. 
V.  The  moth  flying 


454  THE   WONDER  OF  LIFE 

brown  in  colour;  -**ik  a.  large  head  and  a  small  body,  with 

anterior  breathing  tubes,  and  no  open  mouth.    After  a 

few  days  the  ]>'*;•••*  S'?««k  splits  and  the  winged  gnat  escapes. 

Other   Jnaevi*,     No    life-history  is   more   marvellous 

than  that  of  *  «n»th  or  butterfly.     Out  of  the  egg,  after  a 

very  renvt  kv4*  development,  there  emerges  a  minute 

won.!:-lik  •     ^v^^fciittr,  usually  active,  voracious,  and  of 

rapid  Typical!}  ~,  it  shows  a  hard  head  with  biting 

•*<tit  very  minute  antennas,  and  with  several 

*v&  —  in  every  respect  as  different  as  possible 

*-  -     .*i->,;;.rtTO  insect's  head.    The  body  consists  of 

**giuents,  of  which  the  first  three  bear  jointed 

(,  i*«Tesponding  to,  though  they  do  not  become, 

.(eoqoilB  fiiJrumHoA)  HloM  b^H  a'Hjcad  \o  v'toialM  ail  J—  .^  .oil 
.III     .squq   aHT  .11     .ifiKiqistBO  9flT  .1      .namioaqs  B  moil 
}83i  IB  Hloni  9fiT  .VI     ,sni]R-i3fn9  Htom  oH*  rftiw'Bquq 


•rrmvVi   ?r  -....-    ,»-,(  ng   of 

ii!     •:'     «?       iJMSfr  r-  arked 

by  u-apirnU.ry  and  other  diiljt-uiu^s.  -d  by  rapid 

growth.  Finally,  having  reached  its  limit  of  growth, 
the  caterpillar  becomes  quiescent  ;  it  often  surrounds  itself 
with  a  cocoon,  sometimes  silken,  and  passes  into  the 
chrysalis  or  pupa  state.  Serious  respiratory  and  other 
difficulties  beset  the  pupa  ;  a  process  analogous  to  inflam- 
mation pervades  it  ;  the  old  structure  is  broken  down  and 
groups  of  formative  cells  of  an  embryonic  character  proceed 
to  build  up  the  adult  body  on  a  new  architectural  plan. 
Everything  is  changed  —  mouth-parts,  antennae,  food- 
muscles,  everything.  ~.  wad 

compound  eyes,  make  ih<  -  there 

struggles    painfully    out  husk    an 


THE  CYCLE  OF  LIFE  455 

entirely  new  creature,  the  fully -formed  moth  or  butterfly. 
Two  big  facts  stand  out.  The  first  is  that  the  life-history 
is  divided  into  a  feeding  growing  period  and  a  fasting 
reproductive  period.  For  the  amount  that  adult  Lepidop- 
tera  eat  is  trivial,  and  some  have  mouths  that  do  not  open. 
In  no  case  among  the  higher  insects  is  there  any  growth 
after  the  adult  form  is  attained.  The  other  big  fact  is 
the  zig-zagness  of  the  development.  It  proceeds  for  a 
time  along  a  certain  path ;  it  comes  to  a  standstill ;  it 
turns  back  on  itself ;  and  then  it  goes  ahead  once  more 
on  a  quite  different  line. 

Fabre  has  told  us  many  stories  in  regard  to  the  life 
and  habits  of  the  large  plant-bug,  called  Cigale,  famous 
for  its  instrumental  music  and  infamous  for  the  Parthian 
shot  of  noxious  stuff  which  it  delivers  on  our  face  as  it  flies 
away.  The  old  legend  had  it  that  the  Cigale  who  sang 
in  the  summer  was  forced  to  borrow  from  the  ant  when  the 
scarcity  of  winter  came,  but  the  facts  are  the  other  way 
round.  When  all  the  world  is  thirsty  in  the  midsummer 
drought,  the  Cigale  with  its  delicate  auger  broaches  the 
cask  of  a  suitable  shrub.  'Plunging  her  proboscis  into 
the  bung-hole,  she  drinks  deliciously,  motionless,  and  wrapt 
in  meditation,  abandoned  to  the  charms  of  syrup  and  of 
song '.  Many  thirsty  insects  draw  to  the  well,  and  the 
aggressive  ants,  by  sheer  force  of  numbers  and  impudence, 
succeed  in  hustling  the  Cigale  away.  They  then  make  the 
most  of  what  is  left  of  sweet  sap. 

The  eggs  of  the  Cigale  are  laid  about  July,  in  batches 
in  dry  twigs,  ten  or  so  in  each  of  thirty  to  forty  chambers. 
In  autumn  a  remarkable  primary  larva  emerges,  which 
Fabre  compared  to  a  very  minute  fish  with  one  fin — 
the  first  two  legs  being  joined  to  form  the  only  movable 


456  THE  WONDER  OF  LIFE 

appendage.  This  quaint  form  moults  and  there  comes 
forth  a  migratory  larva,  no  bigger  than  a  flea,  which  hangs 
by  its  tail  for  an  hour  or  a  day  at  the  end  of  a  thread,  waving 
its  antennae  and  bending  its  legs.  It  falls  to  the  ground 
and  seeks  for  a  spot  of  pervious  soil  into  which  to  burrow. 
It  becomes  a  deep  burrower  and  taps  the  roots  of  plants, 
probably  remaining,  Fabre  thinks,  for  four  years  under- 
ground. We  venture  to  quote  from  his  Social  Life  in  the 
Insect  World,  the  summing  up  of  this  extraordinary  life- 
history. 

'  Four  years  of  hard  labour  underground,  and  a  month 
of  feasting  in  the  sun  ;  such  is  the  life  of  the  Cigale.  Do 
not  let  us  again  reproach  the  adult  insect  with  his  trium- 
phant delirium.  For  four  years,  in  the  darkness,  he  has 
worn  a  dirty  parchment  overall ;  for  four  years  he  has  mined 
the  soil  with  his  talons,  and  now  the  mud-stained  sapper 
is  suddenly  clad  in  the  finest  raiment,  and  provided  with 
wings  that  rival  the  bird's  ;  moreover,  he  is  drunken  with 
heat  and  flooded  with  light,  the  supreme  terrestrial  joy. 
His  cymbals  will  never  suffice  to  celebrate  such  felicity, 
so  well  earned  although  so  ephemeral '. 

The  common  house-fly  (Musca  domestica)  can  pass  through 
the  whole  of  its  intricate  development — with  three  larval 
stages  and  a  pupal  stage — in  eight  days,  if  the  temperature 
is  steady  and  high  (35°  C.),  but  the  same  process  may  be 
lengthened  out  over  several  weeks.  According  to  Hewitt, 
the  flies  become  sexually  mature  in  10-14  days  after  their 
emergence  from  the  pupa-stage.  Each  fly  lays  from  120-150 
eggs  in  a  single  batch,  and  may  lay  as  many  as  six  batches 
during  its  short  life.  Except  in  warm  stables  and  the  like, 
where  reproduction  may  go  on  practically  without  stopping, 
the  breeding  period  is  usually  from  June  to  October. 


FIG.  75.— Metamorphosis  of  the  common  eel  (Anguilla  vulgaris) 
from  the  knife-blade-like  Leptocephalus  (1)  to  the  shorter 
cylindrical  elver  (5).  (After  Schmid.) 


456  THE  WOXDER  OF  LIFE 

appendage.  This  qu&iut  form  moults  and  there  comes 
forth  a  migratory  !&"<*,  no  bigger  than  a  flea,  which  hangs 
by  its  tail  for  an  hot . .;  *&  a  day  at  the  end  of  a  thread,  waving 
its  antennae  and  K^ding  its  legs.  It  falls  to  the  ground 
and  seeks  for  a  si-  <  of  pervious  soil  into  which  to  burrow. 
It  becomes  a  fk-  %.-  Imrrower  and  taps  the  roots  of  plants, 
probably  reins*  wig,  Fabre  thinks,  for  four  years  under- 
ground. We  ^.tiMire  to  quote  from  his  Social  Life  in  the 
Insect  Wc-r*>,i'._  i'te  summing  up  of  this  extraordinary  life- 
history. 

<*»»  of  hard  labour  underground,  and  a  month 

' .-  *-  •  •  •  -,  *  the  sun  ;  such  is  the  life  of  the  Cigale.    Do 

>**in  reproach  the  adult  insect  with  his  trium- 

filluigfiA)  fe»  nomrnoo  aril  to  auoHqionjBisM— XV  .oil 
Mil  ol  (I)   auififiqaaoJqaJ   Mlil-abald-afcijpl  aril  rnoit 
/  (.bimibS  «\\N)    •(C)«y[3,l!3gp|g 

wings  that  rival  *  with 

heat  and  flooded    <  joy. 

Hia  cyn.h,:-.-  ?.;;;  y.,  -  ch  felicity, 

so  well  earned  althi'  il\ 

The  common  house-fly  (Mttsco  domestica)  can  pass  through 
the  whole  of  its  intricate  development — with  three  larval 
stages  and  a  pupal  stage — in  eight  days,  if  the  temperature 
is  steady  and  high  (35°  C.),  but  the  same  process  may  be 
lengthened  out  over  several  weeks.  According  to  Hewitt, 
the  flies  become  sexually  mature  in  10-14  days  after  their 
emergence  from  the  pupa-stage.  Each  fly  lays  from  120-150 
eggs  in  a  single  batch,  and  may  lay  as  many  as  six  batches 
during  its  short  life.  Except  in  warm  stables  and  the  like, 
where  reproduction  may  go  on  practically  wi 
the  breeding  period  is  usually  from  «h 


THE  CYCLE  OF  LIFE  457 

There  is  a  rather  famous  Aphis — Schlechtendalia  chinensis 
— which  makes  galls  on  Rhus  semi-alata  in  Japan  and 
China.  The  galls  are  used  in  dyeing  and  tanning — they 
are  rich  in  tannin,  and  in  former  times  they  served  the 
Japanese  women  as  a  tooth-powder  for  blackening  their 
teeth.  Sasaki  has  almost  cleared  up  its  complicated  life- 
history.  There  is  a  succession  of  wingless  females,  partheno- 
genetic  and  viviparous,  and  after  a  time  winged  females 
appear  which  lay  eggs  containing  well-advanced  embryos. 
These  develop  into  wingless  females  again.  No  males 
have  been  found,  and  we  have  a  glimpse  of  a  possible 
continuous  Parthenopeia. 

Sometimes  the  life-cycle  is  long  drawn  out,  as  in  the  case 
of  the  seventeen-year  cicadas  (Tibicina  septendecim),  well 
known  in  the  United  States,  where  they  are  often  called 
'  locusts  '.  (A  small  British  relative,  Cicadetta  montana,  is 
sometimes  found  in  the  New  Forest.)  The  peculiarity 
of  the  Cicada  is  that  it  is  specially  abundant  every  seven- 
teenth year  in  the  northern  States,  or  every  thirteenth 
year  in  the  southern  States.  The  eggs  are  laid  on  the 
twigs  of  trees ;  the  larvae  drop  to  the  ground  and  cluster 
on  the  roots,  sucking  the  sap ;  after  a  prolonged  larval 
period,  there  is  short  pupation,  and  a  broad,  black  insect, 
with  reddish  nervures  on  its  wings,  emerges.  The  loud 
instrumental  music  or  stridulation  made  by  the  males  is 
very  familiar. 

Tunicates. — The  majority  of  Tunicates,  belonging  to 
the  Ascidian  type,  are  somewhat  nondescript  marine 
animals,  of  sedentary  habit,  often  compared  to  wine-skins 
or  leather  water-bottles.  Until  their  development  was 
made  known,  no  one  suspected  that  their  relationships 
were  with  backboned  animals.  The  egg  develops  into  a 


458  THE  WONDER  OF  LIFE 

minute  transparent  free-swimming  larva,  suggestive  of  a 
tadpole.  For  some  hours  it  enjoys  a  free-swimming  life, 
propelling  itself  by  means  of  its  tail.  At  this  stage  it  has  a 
brain  and  a  delicate  dorsal  nerve-cord,  a  supporting  dorsal 
axis  (or  notochord)  in  its  tail,  a  brain-eye,  a  ventral  tubular 
heart,  and  two  or  more  pharyngeal  gill-slits — all  of  them 
distinctively  vertebrate  characters.  But  it  does  not  fulfil 
the  promise  of  its  youth  !  It  soon  gives  up  its  active  life, 
fastens  itself  by  its  head  to  seaweed  or  stone,  and  almost 
immediately  falls  victim  to  rapid  degeneration.  The 
nerve-cord  is  lost  and  the  brain-eye ;  the  tail  shrinks  and 
disappears,  devoured  by  its  own  phagocytes  ;  the  posterior 
part  of  the  body  becomes  twisted  dorsally  through  180° — 
and  within  a  few  hours  the  creature  begins  to  look  like  a 
miniature  Ascidian — one  of  the  most  signal  instances  of 
individual  degeneration  in  the  whole  animal  kingdom. 

Eels. — There  is  a  fascination  in  the  life- history  of 
the  freshwater  eel,  though  the  mystery  has  been  in  part 
removed.  From  inland  ponds  and  quiet  stretches  of  rivers 
the  full-grown  eels  migrate  on  autumn  nights  seawards ; 
they  pass  out  to  sea  into  deep  water,  and  probably  die  after 
reproduction,  for  they  never  return.  Obscurity  still  hangs 
over  the  deposition  and  fertilization  of  the  eggs  and  over 
the  early  stages  of  development.  The  transparent  Lepto- 
cephalus  larvae  are  found  near  the  surface,  and  are  for  a 
year  or  more  pelagic.  From  the  open  sea,  the  young  eels, 
when  they  have  become  cylindrical  in  shape,  migrate 
shorewards  and  pass  up  the  streams  in  a  marvellous 
procession  or  eel-fare. 

On  the  Michael  Sars  (1910)  expedition,  the  larvae  of  the 
common  eel  were  found  not  only  on  the  Continental  slopes, 
but  also  in  mid-ocean  over  the  greatest  depths,  both  over 


THE  CYCLE  OF  LIFE  459 

the  deep  eastern  and  western  basins  and  over  the  Azores 
ridge  separating  them.  The  larger  larvae  were  all  got 
north  of  the  Azores,  and  the  younger  stages  were  all  found 
south  of  the  Azores,  which  led  Dr.  Hjort  to  suggest  that 
the  spawning  area  is  probably  in  the  southern  central  part 
of  the  North  Atlantic.  No  transformation-stages  were 
found  in  mid-ocean,  and  it  may  be  that  the  change 
only  occurs  on  the  Continental  slope.  But  it  must 
always  be  remembered  that  the  developing  eggs  have  not 
yet  been  discovered. 

The  Salmon. — In  British  rivers,  the  time  of  salmon 
spawning  is  in  the  late  autumn  or  winter.  The  eggs  are 
laid  in  the  gravelly  bed  of  the  stream,  and  they  develop 
very  slowly.  After  three  or  four  months  the  egg-envelope 
bursts  and  the  larva  is  set  free,  still  encumbered  with  a 
large  yolk-sac,  on  the  contents  of  which  it  subsists  for  about 
seven  weeks.  About  the  eighth  week  after  hatching,  the 
supply  of  yolk  is  exhausted,  and  the  *  fry  '  — about  an  inch 
long — begin  to  fend  for  themselves  and  to  move  energetic- 
ally. They  grow  by  the  end  of  the  year  to  be  somewhat 
trout-like  '  parr  ',  about  four  inches  long.  In  their  second 
year,  usually,  the  young  salmon  change  in  coloration, 
donning  a  beautiful '  sea-jacket,'  and  are  known  as  '  smolts ' 
— six  or  seven  inches  in  length.  These  go  down  to  the  sea, 
feed  voraciously,  grow  rapidly,  accumulate  stores,  and 
become  grilse.  After  a  variable  period  of  feeding  and 
growing,  which  may  last  a  year  or  two  years  or  more,  they 
are  ready  to  spawn,  and  return  to  the  place  of  their  birth 
in  the  fresh  waters.  Such  in  outline  is  the  typical  life- 
history  of  the  salmon,  but  there  are  many  variations  on 
this  theme.  We  have  described  in  our  Biology  of  the  Seasons 
the  journey  up  the  rivers,  the  struggle  against  the  stream 


460  THE  WONDER   OF  LIFE 

and  the  leaping  of  the  falls — all  implying  efforts  which  are 
the  more  remarkable  since  there  seems  to  be  no  evidence 
that  the  adult  salmon  ever  feeds  in  fresh  water.  Few  salmon 
seem  to  spawn  more  than  once,  and  some  die  of  spawning. 
It  is  of  interest  to  contrast  the  eel  and  the  salmon,  for  the 
former  is  a  marine  fish  which  has  taken  secondarily  to  a 
life  in  the  rivers  and  ponds,  while  the  latter  is  primarily  a 
freshwater  fish  which  has  taken  to  the  exploitation  of 
the  sea. 

In  the  case  of  the  Pacific  salmon  (Oncorhynchus)  the 
general  facts  are  the  same,  but  a  simplification  is  implied 
in  the  fact  that  the  adults  die  after  spawning  once.  They 
do  not  return  to  the  sea.  The  run  up  the  rivers  to  the 
spawning  grounds  several  hundred  miles  off  is  very 
remarkable ;  it  may  occupy  two  or  three  months  ;  after 
tidal  waters  are  passed  the  fish  continues,  according  to  Pro- 
fessor C.  W.  Greene's '  marking  '  experiments,  at  an  average 
speed  of  not  less  than  7£  miles  a  day  ;  all  the  work  is  done 
on  an  empty  stomach,  for  feeding  stops  absolutely  in  fresh 
water ;  the  work  often  includes  jumping  six  or  seven  feet 
in  height  and  then  continuing  against  a  swift  rush  of  water  ; 
and  all  the  time  the  reproductive  organs  are  growing  rapidly 
at  the  expense  of  other  parts  of  the  body.  It  is  a  remarkable 
performance. 

Frogs. — Out  of  the  frog's  egg,  in  the  midst  of  its 
enveloping  sphere  of  jelly,  there  emerges  a  ciliated  larva, 
which  has  already  had  an  embryonic  development  of  about 
a  fortnight.  It  is  mouthless  and  limbless  ;  the  eyes  growing 
out  from  the  brain  have  not  yet  reached  the  surface  ;  there 
are  the  beginnings  of  external  gills  ;  and  there  is  a  glandular 
cement  organ  on  the  under  surface  of  the  head,  by  means 
of  which  the  larva  attaches  itself  to  water -weed  and  other 


THE  CYCLE  OF  LIFE  461 

objects.  The  gills  become  branched  ;  the  mouth  opens  ; 
the  food-canal  lengthens  till  it  is  like  a  watch-spring  ; 
four  gill-clefts  open  from  the  pharynx  to  the  exterior ; 
the  larvae  feed  greedily  on  vegetable  matter,  and  grow 
rapidly  ;  as  their  power  of  locomotion  increases,  the  cement 
organs  dwindle. 

The  true  tadpole  stage  then  begins.  A  skin-fold  covers 
the  gills,  which  are  absorbed,  only,  however,  to  be  replaced 
by  a  second  very  similar  set.  Both  sets  are  comparable  to 
the  external  gills  of  the  double-breathing  lung-fishes  (or 
Dipnoi)  rather  than  to  the  gills  of  ordinary  fishes.  The 
mouth  acquires  horny  jaws  and  the  fleshy  lips  bear  horny 
papillae.  A  gill-chamber  is  formed  on  each  side,  with  one 
exhalant  opening,  however,  to  the  left.  The  circulation 
is  like  that  of  a  fish,  and  the  heart  is  two-chambered ; 
the  tadpole  is  about  a  month  old.  The  third  period  is 
marked  by  the  appearance  of  the  limbs  and  by  the 
development  of  the  lungs.  The  tadpoles  come  to  the  sur- 
face to  take  gulps  of  air ;  the  circulation  ceases  to  be 
piscine  ;  the  heart  becomes  three-chambered  ;  the  tadpole 
is  two  months  old. 

The  tadpole  reaches  its  full  size,  and  the  metamorphosis 
is  close  at  hand.  It  seems  to  fast,  but  the  tail,  which  under- 
goes internal  dissolution,  furnishes,  through  the  medium 
of  the  amoeboid  phagocytes,  some  nourishment  to  other 
parts  of  the  body.  The  horny  jaws  are  lost ;  the  frilled 
lips  shrink ;  the  hitherto  rounded  mouth  becomes  frog- 
like  ;  the  tongue  enlarges  and  gains  mobility  ;  the  eyes  are 
exposed  ;  the  fore-limbs,  which  have  been  kept  back  by  the 
gill-cover,  become  free.  The  animal  recovers  its  appetite, 
becomes  thoroughly  carnivorous,  gets  a  relatively  shorter 
intestine,  has  its  hind  legs  relatively  lengthened,  and,  having 


462  THE  WONDER  OF  LIFE 

lost  all  trace  of  its  tail,  hops  ashore  a  little  frog — about 
three  months  old. 

It  is  very  interesting  to  observe  that  in  this  single  life- 
history  there  is  first  of  all  nutritive  dependence  on  the 
legacy  of  yolk,  then  a  period  of  vegetarian  diet,  then  a 
somewhat  omnivorous  period,  then  a  fast,  then  a  carnivor- 
ous time,  and  finally  an  insectivorous  adult  lif e.  Similarly, 
as  regards  respiration,  there  is  great  variety.  The  newly- 


FIG.  76. — Male  Edible  Frog,  Rana  esculenta,  showing  the  resonating 
,  sacs  protruded  from  the  corners  of  the  mouth.  From  a  specimen. 

hatched  larva  breathes  through  its  skin  ;  it  has  a  first  set 
of  gills  ;  it  develops  gill-clefts  ;  a  second  set  of  gills  arising 
under  the  gill-covering  replaces  the  first  set ;  when  it  is 
two  months  old  it  breathes  by  both  gills  and  lungs  ;  the 
gills  disappear  and  the  frogling  is  a  lung-breather  ;  but 
all  through  the  winter  the  frog  harks  back  to  the 
primitive  cutaneous  respiration. 

As  regards  recapitulation,  it  goes  without  saying  that 


THE   CYCLE  OF  LIFE  463 

the  larval  frog  is  never  like  a  young  fish.  It  has  no  scales, 
for  instance,  nor  fin-rays  supporting  the  tail- fin,  and  there 
are  much  more  fundamental  differences.  It  is  an  Amphib- 
ian from  first  to  last.  And  yet,  if  we  fix  our  attention  on 
the  development  of  the  heart  or  the  circulation,  we  must 
admit  that  the  tadpole  passes  through  stages  which  are 
permanent  in  fishes.  In  other  parts  of  its  organogenesis 
it  climbs  up  its  own  genealogical  tree,  and  to  this  extent 
at  least  confirms  the  '  Recapitulation  Doctrine '. 

It  is  very  instructive  to  compare  the  long  drawn  out  life- 
history  of  the  common  frog  with  that  of  some  of  its  relatives. 
In  the  Surinam  toad  (Pipa)  and  in  some  Tree- Frogs,  the 
tadpole  stage  is  skipped  altogether,  while  in  the  Paradoxical 
Frog  (Pseudis  pamdoxa)  the  tadpole  stage  is  much  more 
impressive,  at  any  rate,  than  the  adult.  In  his  delightful 
Infancy  of  Animals,  Mr.  W.  P.  Pycraft  tells  us  that  the 
tadpole  is  nearly  a  foot  long,  nine  inches  going  to  the  enor- 
mous tail,  and  three  inches  to  the  head  and  trunk.  During 
a  prolonged  fast,  and  after  no  little  re-modelling,  this  huge 
larva  is  shaped  into  an  adult  frog,  only  two  and  a  half  inches 
in  length. 

Retrospect. — The  general  idea  which  these  life- histories 
suggest,  is  that  the  various  chapters  of  a  typical  life- 
history  are  capable  of  being  lengthened  out  or  shortened 
down  according  to  the  conditions  of  life ;  and  to  some 
extent,  also,  that  particular  conditions  of  life,  may  have 
been  sought  out  to  suit  particular  forms  of  the  life-curve. 
The  various  arcs  on  the  span  of  life  are,  so  to  speak,  elastic. 
The  line  of  life  is  like  a  telescope  with  many  joints  ;  it  can 
be  drawn  out  to  its  full  length ;  it  can  be  pushed  in  to  a 
minimum ;  or  one  part  can  be  lengthened  and  another 
shortened.  Just  as  some  flowers  remain,  as  it  were,  per- 


464  THE  WONDER  OF  LIFE 

manent  buds,  so  some  animals  remain  always  young. 
In  what  is  called  paedogenesis,  sometimes  illustrated  by 
the  Axolotl,  even  the  reproduction  is  shunted  back  into 
larval  life,  so  that  adult  life  is  reduced  to  nil.  In  other 
cases,  the  conditions  of  adult  life  are  extremely  riskful, 
and  its  duration  is  contracted  to  a  few  weeks  or  days  or 
even  hours !  In  other  cases,  it  is  the  larval  life  that  is 
condensed  ;  thus  in  the  freshwater  crayfish,  what  comes 
out  of  the  egg  is  practically  a  miniature  adult ;  all  the 
usual  larval  stages,  so  characteristic  of  higher  crustaceans, 
have  been  telescoped  into  the  embryonic  development  with- 
in the  egg.  Or  it  may  be  that  the  larval  life  is  drawn  out 
for  years.  The  idea  should  be  linked  on  to  what  has  been 
noted  in  regard  to  the  successive  chapters  in  the  routine  of 
parental  behaviour  (see  p.  430).  It  is,  in  a  word,  the  idea  of 
temporal  variations,  that  the  life-histories  of  animals  are 
like  tunes,  which  may  be  much  altered  by  playing  one  part 
out  of  all  proportion  slowly,  and  another  part  very  quickly. 
We  may  even  go  further,  and  recognize  that  there  are 
youthful  types  of  organisms  and  others  which  are  born  old. 
But  this  is  the  beginning  of  another  story. 

The  Story  of  Niners. — A  score  of  miles,  as  the  crow 
flies,  from  the  sea,  there  is  a  stretch  of  slowly -flowing  river, 
from  which  a  mill-race  has  borrowed  most  of  the  water. 
There  are  many  pools  with  sand  or  mud,  and  if  this  be 
stirred,  we  get  a  glimpse  of  curious,  sluggish,  eel-like  crea- 
tures, variously  known  as  niners,  or  prides,  or  larval 
lampreys.  Some  four  to  six  inches  long  at  the  end  of  their 
fluviatile  life,  with  a  polished  dark  skin,  with  a  horse-shoe 
lip  around  a  toothless  mouth,  they  are  jawless,  limbless, 
and  scaleless,  and  therefore  cannot  be  ranked  as  fishes. 
Although  they  are  called  '  niners  '?  i.e.  nine-eyes  (German, 


THE  CYCLE  OF  LIFE  465 

Neunaugen],  they  are  blind ;  for  their  eyes,  growing  out  from 
the  brain  as  vertebrate  eyes  always  do,  have  not  yet  reached 
the  surface.  There  are  seven  gill-slits  on  each  side,  and 
these  have  been  popularly  counted  in  as  eyes.  These 
curious  old-world  creatures  are  often  regarded  as  the  young 
of  eels,  but,  as  a  matter  of  fact,  they  are  far  below  the  level 
of  fishes  on  the  genealogical  tree  of  animals.  Whence  have 
they  come  and  what  future  is  before  them  ? 

The  Sea  Lamprey  (Petromyzon  marinus),  whose  larvae 
the  niners  are,  is  a  strong  muscular  animal,  sometimes  a 
yard  long,  abundant  in  the  Mediterranean  and  the  North 
Atlantic.  It  also  occurs  in  the  American  lakes,  having  in 
this  case  dispensed  with  its  normal  journey  to  the  sea. 
The  colour  is  greyish  green  with  darker  spots.  The  struc- 
tural peculiarities  are  numerous.  For  apart  from  the 
absence  of  jaws,  limbs,  and  scales,  which  we  have  already 
mentioned,  there  is  a  circular  adhesive  disc  around  the 
mouth  and  lined  with  rows  of  horny  teeth,  there  is  a  very 
muscular  protrusible  '  tongue '  bearing  horny  plates  for 
rasping  with,  there  is  an  unpaired  nostril  far  back  on 
the  top  of  the  head,  like  a  porpoise's  blow-hole,  and  there 
are  curious  gill-purses.  Their  habits  are  not  less  remark- 
able. They  attach  themselves  to  living  fishes  and  rasp 
the  flesh  and  suck  the  blood.  They  take  a  very  firm  hold 
of  their  victims  and  make  deep  holes,  and  they  are  some- 
times carried  for  long  distances  by  large  fishes,  such  as 
salmon.  They  migrate  in  spring  or  early  summer  from 
the  sea  (or  the  lakes  of  the  State  of  New  York)  to  the  rivers, 
usually  changing  to  a  more  yellowish  colour ;  they  make 
nests  of  stones,  and  they  die  after  spawning.  * 

It  is  a  very  general  fact  of  Natural  History  that  when 
the  habitats  of  adult  and  young  are  different,  the  cradle- 

H  H 


466  THE  WONDER  OF  LIFE 

area  represents  the  old  home.  The  salmon  is  essentially 
a  freshwater  fish,  though  its  nutritive  periods  are  mostly 
spent  in  the  sea.  Its  spawning  in  the  rivers  is  indicative 
of  its  original  home.  The  common  eel,  on  the  other  hand, 
which  has  its  nutritive  period  in  the  fresh  waters,  goes 
down  to  the  Deep  Sea  to  spawn,  and  is  probably  to  be 
regarded  as  essentially  a  marine  fish  with  its  old  home 
in  the  greater  depths.  A  similar  argument  leads  to  the 
view  that  the  Sea-Lamprey  is  primarily  a  freshwater  fish 
which  has  secondarily  taken  to  spending  a  nutritive  period 
in  the  sea.  We  have  already  spoken  of  the  forms  of 
Petromyzon  marinus  in  lakes  of  the  State  of  New  York, 
which  do  not  leave  the  fresh  water  at  all,  though  they 
migrate  from  lake  to  river  to  spawn.  In  the  case  of  the 
River  Lampern  (Lampetra  fluviatilis),  whose  young  are 
also  called  '  niners ',  some  remain  all  their  lives  in  fresh 
water,  while  others  go  down  to  the  sea.  This  is  paralleled 
by  the  Trout  (Salmo  trutta),  some  forms  of  which  remain 
in  lakes  and  rivers,  while  others  (distinguished  nominally 
as  Sea-trout)  go  down  to  the  sea.  It  must  also  be  noted 
that  a  number  of  species  of  lamprey,  such  as  the  Brook 
Lamprey,  never  leave  the  fresh  water,  and  this  may  be 
taken  as  another  argument  in  support  of  the  view  that 
the  Sea  Lamprey  is  secondarily  marine.  Let  us  follow 
them  now  on  their  return  journey  to  their  cradle-area. 
The  spawning  of  the  Sea  Lamprey  has  been  well  described 
by  Dr.  L.  Hussakof .  A  circular  depression  is  made,  two  to 
three  feet  in  diameter,  in  the  river-bed.  Large  numbers  of 
pebbles  and  stones  are  carried  out  of  the  chosen  area  until 
a  shallow  basin  is  formed,  naturally  with  a  floor  of  sand 
and  fine  gravel.  The  adhesive  disc  around  the  mouth 
acts  like  a  vacuum-sucker,  and  it  can  be  made  to  '  work  ' 


JFlG.  77. — Marine  Lampreys  (Petromyzon  mannus),  making  a  nest 
in  a  stream,  removing  the  larger  stones  from  a  selected  spot  and 
piling  them  around  the  circumference. 


BONDER   OF  LIFE 

area  represent*  •  fce-    M  home.     The  salmon  is  essentially 

a  freshwater  n*t    iJtoagh  its  nutritive  periods  are  mostly 

spent  in  the  >••"?-      H,«  spawning  in  the  rivers  is  indicative 

of  its  origin^  >w  The  common  eel,  on  the  other  hand, 

which  has  fc&tive  period  in  the  fresh  waters,  goes 

down  to  >  $?&  to  *ipawn,  and  is  probably  to  be 

regarded  -<vr»alJy  a  marine  fish  with  its  old  home 

ii-fcchs.     A  similar  argument  leads  to  the 

;«tst- Lamprey  is  primarily  a  freshwater  fish 

ujNiftiy  tak*M»  to  spending  a  nutritive  period 

W>  have  air* fc--*v  spoken  of  the  forms  of 

*  fcfcfce  «v         '  :•-•  -i-AWf;      In  the  case  of  the 
B  gnblem  feuaiiBm  nos^moDa^)  8/aiqm 
bns  Joqa  balosba  £  moil  eanote  ISBIB!  aril  ^nr/omai 

.sonaialmuDiio  artl  bnuoie  mal 

remain 
.-•}  nominally 

•  -ri  r-  ,«!>)  ,  ...st  fclso  be  noted 

•-liAt.  *  n«r»b«r  of  sp^es  of  lamprey,  such  as  the  Brook 
Lamprey,  rwv«r  leave  the  fresh  water,  and  this  may  be 
taken  as  a-K'tht/r  argument  in  support  of  the  view  that 
the  Sea  Liimfsrey  is  secondarily  marine.  Let  us  follow 
them  now  on  their  return  journey  to  their  cradle-area. 
The  spawning  of  the  Sea  Lamprey  has  been  well  described 
by  Dr.  L.  Hussakof .  A  circular  depression  is  made,  two  to 
three  feet  in  diameter,  in  t  \\*  river-bed.  Large  numbers  of 
pebbles  and  stones  a^  at  of  the  chosen  area  until 

A  *feaUow  basin  is  in.  y  with  a  fr 

HM-.  .  avel.     '; 

:-:;;i   •    n  ':  >VOrk  ' 


X^cT^   , 


THE   CYCLE   OF  LIFE  467 

after  the  animal  is  dead.  Both  sexes  work  at  the  nest- 
making,  and  the  males  sometimes  make  considerable 
preparations  before  the  females  arrive  on  the  scene. 
Sometimes  two  lampreys  will  unite  their  energies  in  lifting  a 
heavy  stone. 

When  the  nest  is  ready,  or  while  it  is  being  prepared, 
the  female  lamprey  lays  her  eggs  within  the  circle,  clinging 
as  she  does  so  to  a  large  stone.  At  the  same  time  the  male 
seizes  her  by  the  top  of  the  head,  and  the  two  bodies  are 
very  rapidly  vibrated  for  two  or  three  seconds,  during  which 
the  milt  or  seminal  fluid  is  shed  upon  the  eggs.  Fertiliza- 
tion is  external.  The  same  remarks  might  be  made  in 
regard  to  the  brook-lampreys — Lampetra  planeri  in  Europe 
and  Lampetra  wilderi  in  North  America.  '  The  females/ 
according  to  Forbes  and  Kichardson,  '  spawn  in  shallow 
water,  and,  as  a  rule,  where  there  is  some  current  over 
pebbly  or  stony  bottom  near  the  headwaters  of  a  stream. 
During  the  spawning  process  the  females  cling  with  their 
oval  mouths  to  pebbles  or  stones,  and  are  clasped  at  the 
nape  by  the  suctorial  discs  of  the  males  '.  In  the  case 
of  the  river  lamprey,  a  good  many  couples  combine  to  make 
the  nest  and  use  it  in  common.  The  surface  of  the  eggs 
is  covered  with  an  adhesive  stuff,  to  which  sand  grains 
adhere,  so  that  the  eggs  sink.  Moreover,  they  say  that 
the  two  parents  proceed  at  once  to  loosen  some  stones  at 
the  upstream  side  of  the  nest,  so  that  the  loosened  sand 
buries  the  eggs.  There  may  be  several  spawnings  at  short 
intervals,  and  then  the  parents  pass  down  stream  to  die. 
For  that  is  the  most  remarkable  fact  in  the  story  of  the 
lampreys,  that  the  one  generation  comes  to  an  end  in  giving 
the  next  generation  a  beginning.  Reproduction  is  often 
the  beginning  of  death,  but  here  the  end  comes  quickly. 


468  THE  WONDER  OF  LIFE 

We  are  familiar  with  this  in  some  lower  animals,  such  as 
May-flies  and  butterflies,  and  in  some  still  lower  animals, 
such  as  some  of  the  worms,  but  it  is  rather  startling  to  find 
a  big  muscular  sea  lamprey — a  yard  long  and  as  thick  as  a 
lady's  wrist — dead  and  stranded  in  the  shallow  water  of 
the  river  not  far  below  the  spawning-place.  What  does 
it  all  mean  ?  Uprooting  and  transporting  the  stones  has 
involved  no  small  expenditure  of  energy,  no  little  wear  and 
tear ;  the  skin  is  often  bruised  and  cut  (and  there  are 
wounds  of  combat  and  of  mating  besides) ;  Bacteria  and 
Fungi  begin  to  settle  down  (to  which  the  skin  of  the  larva 
seems  to  be  immune  because  of  a  ferment  it  possesses) ; 
the  creatures  become  blind  and  emaciated,  and  are  often 
attacked  by  other  lampreys.  But  all  the  external  causes 
added  up  will  not  account  for  the  wiping  out  of  the  adult 
lampreys  after  spawning.  Every  one  agrees  that  these 
are  contributory  or  accessory,  but  not  the  essential  causes 
of  death. 

A  deeper  answer  is  to  be  found  in  the  fundamental 
antithesis  between  nutrition  and  reproduction.  These 
sexually  mature  lampreys  have  not  been  feeding  at  all : 
their  hunger  has  been  devoured  by  love.  Profound  bodily 
changes  have  been  associated  with  the  reproductive  func- 
tion, similar  to  those  more  familiar  in  the  case  of  the  salmon. 
The  intestine,  for  instance,  is  quite  out  of  gear.  Deeper  still, 
perhaps,  it  is  possible  to  go,  for  it  seems  legitimate  to 
suppose  that  the  length  of  life's  tether  is,  in  many  cases  at 
least,  adaptive.  Where  reproduction  takes  such  a  grip 
of  the  constitution,  it  would  not  be  well  for  the  race  that 
there  should  be  survival.  In  other  words,  those  of  a  type 
that  tended  to  live  longer,  but  with  enfeebled  energies, 
have  been  eliminated  in  the  course  of  Natural  Selection. 


THE  CYCLE  OF  LIFE  469 

But  let  us  return  to  the  fertilized  eggs.  They  develop 
quickly  and  hatch  in  about  a  fortnight.  About  a  month 
later,  when  about  half  an  inch  long,  the  larvae  leave  the 
nest  and  seek  out  quiet  stretches  of  the  river.  They  differ 
from  the  adults  in  the  horseshoe  shape  of  the  lips,  in  having 
a  sieve  of  barbels  guarding  the  true  mouth,  in  the  details 
of  their  respiratory  system,  in  having  much  less  developed 
unpaired  fins,  and  in  being  blind.  They  form  burrows 
in  the  sand  or  mud,  and  feed  on  small  aquatic  animals. 
It  is  very  difficult  for  ordinary  eyes  to  see  any  difference 
between  the  larvae  of  the  various  species,  and  the  technical 
name  Ammoccetes  branchialis  is  applied  to  them  all. 

After  three  or  four  years  of  a  somewhat  monotonous 
juvenile  life,  the  larvae  begin  to  grow  up.  They  put 
away  their  larval  characters  and  pass  through  a  metamor- 
phosis, just  as  a  tadpole  does  in  turning  into  a  frog.  This 
is  accomplished  in  the  autumn  months  between  the  end  of 
August  and  mid-October.  The  horseshoe  lips  are  changed 
into  a  circle,  the  barbels  into  papillae,  the  suctorial  disc  is 
formed,  the  teeth  develop,  internal  adjustments  are  effected, 
the  creatures  become  more  active,  and  pass  down  the  rivers 
to  the  sea  or  the  great  lake,  where  they  become  strictly 
fish-eaters.  After  two  or  three  years  of  vigorous  life  and 
rapid  growth  the  young  lampreys  have  quite  grown  up, 
and  they  return  up  the  streams  to  their  old  cradle-area, 
which  is  also  the  place  of  their  death. 

A  Strasburg  fisherman  called  Baldner  is  said  to  have 
convinced  himself  more  than  two  hundred  years  ago  that 
*  niners '  grew  into  lampreys,  but  his  correct  conclusion 
was  not  accepted  till  1826,  when  A.  Miiller  observed  the 
whole  life-history  of  the  brook  lamprey — the  eggs  develop- 
ing into  niners,  and  these  changing  into  the  adult  forms. 


470  THE  WONDER  OF  LIFE 

The  lampreys  have  many  primitive  features,  e.g.  in 
their  vertebral  axis,  their  skull,  their  nasal  passage,  and 
they  are  without  doubt  very  old-fashioned  types.  They 
probably  diverged  from  the  vertebrate  stock  before  the 
evolution  of  definite  jaws,  but  it  is  possible  that  they  long 
ago  lost  the  jaws  which  their  remote  ancestors  had.  Con- 
sistent with  their  old-fashioned  character  is  the  poorly- 
developed  brain,  and  the  low  order  of  intelligence  that 
they  exhibit.  Bashford  Dean  and  R  B.  Sumner  have 
noticed  that  many  of  the  movements  of  brook  lampreys 
are  not  very  *  purposelike ',  and  Hussakof  remarks  the 
same  defect  in  the  sea-lamprey.  '  Thus  a  lamprey  will 
sometimes  pick  up  a  stone  outside  the  nest,  carry  and 
drop  it  into  the  nest ;  or  while  carrying  out  a  stone  will 
drop  it  half-way  up  the  side  of  the  nest.  It  will  tug  at  a 
large  stone  which  it  cannot  possibly  dislodge,  or  at  a  log, 
in  an  effort  to  drag  it  out  of  the  nest,  and  will  repeat  this 
again  and  again,  without  profiting  in  the  least  by  previous 
failures.  On  the  whole,  one  has  a  feeling  that  the  lamprey 
possesses  a  very  low  mentality,  even  as  compared  with 
fishes '.  They  seem  to  be  guided  greatly  by  touch,  and 
they  exhibit  a  curious  preoccupation  with  their  work, 
paying  no  heed,  for  instance,  to  onlookers  or  to  the  noise  of 
automobiles  clattering  over  a  wooden  bridge  above  the 
nest-building.  But  whether  this  apparent  absorption  in 
their  work  may  be  due  to  sensory  dullness,  we  do  not  at 
present  know.  In  any  case,  stupid  or  not,  these  old-world 
creatures  do  not  choose  the  path  of  least  resistance  ;  alike 
in  their  migrations  and  in  their  nest-buildings  they  afford 
us  abundant  food  for  wonder. 


CHAPTER  VII 

THE  WOKDEK  OF  LIFE 

(CHARACTERISTICS  OF  LIVING  CREATURES) 

'  past  ano  future  are  unknown  to  ber.  £be  present  is  ber 
eternity.  Sbe  is  beneficent.  .  .  ,' 

4  Sbe  is  complete,  but  never  finfsbeo.  Bs  sbe  works  now, 
so  can  sbe  always  work.  .  .  / 

'  Sbe  is  ever  sbaping  new  forms ;  wbat  is,  bas  never  p.et 
been ;  wbat  bas  been,  comes  not  again.  3£verp.tbin0  is  new, 
ano  set  naugbt  but  tbe  olo.' 

— Goethe's  Aphorisms,  translated  by  Huxley. 

The  Creature  Itself — Organisms  and  Mechanisms — The  Insignia 
of  Life — Down-breaking  and  Up-building — The  Power  of 
Growing — Capacity  for  Behaviour — Power  of  Reproducing — 
Development — Variability — Simulacra  Vitse — Difficult  Pheno- 
mena— The  Powers  of  Life — Correlation — The  Subtlety  of  Life — 
Adaptation — Regeneration — The  Crowning  Wonder  of  Evolu- 
tion— Vitalism. 

WE  have  considered  organisms  as  actors  in  a  drama, 
living  in  haunts,  conquering  space,  trading 
with  time,  and  passing  from  phase  to  phase  in  their  indivi- 
dual life-histories.  Let  us  now  change  our  point  of  view 
and  think  of  the  living  creature  itself.  What  are  the  great 
facts  in  regard  to  it  and  its  living  that  stand  out  when  we 
get  to  a  little  distance,  and  are  not  embarrassed  by  the 
details  of  anatomy,  physiology,  embryology  and  the  like  ? 

THE  CREATURE  ITSELF 

Were  it  not  for  the  difficulty  of  seeing  things  clearly, 
thoroughly,  and  imaginatively,  all  educated  men,  with 

471 


472  THE  WONDER  OF  LIFE 

opportunities  of  enjoying  the  observation  of  life  as  it  is 
lived  in  Nature,  would  be  unanimous  in  admiration  of 
every  living  creature.  The  normal  outlook,  admittedly 
difficult  to  attain  to,  is  expressed  in  Walt  Whitman's  well- 
known  creed  : — 

4 1  believe  a  leaf  of  grass  is  no  less  than  the  journey- work  of  the 

stars, 
And  the  pismire  is  equally  perfect,  and  the  grain  of  sand,  and  the 

egg  of  the  wren, 

And  the  tree-toad  is  a  chef-d'oeuvre  for  the  highest, 
And  the  running  blackberry  would  adorn  the  parlours  of  heaven, 
And  the  narrowest  hinge  in  my  hand  puts  to  scorn  all  machinery, 
And  the  cow  crunching  with  depressed  head  surpasses  any  statue, 
And  a  mouse  is  miracle  enough  to  stagger  sextillions  of  infidels.' 

Organisms  and  Mechanisms. — Both  in  teaching  and 
in  investigation  it  is  very  useful  to  compare  living  creatures 
to  engines.  Both  are  material  systems  for  the  transforma- 
tion of  matter  and  energy.  But  the  analogy  is  most 
useful  when  it  breaks  down,  for  then  the  insignia  of  life 
stand  out  in  relief.  Professor  Joly  long  ago  pointed  out  one 
of  the  deep  differences  between  an  inanimate  material 
system  and  a  living  organism : 

'  While  the  transfer  of  energy  into  any  inanimate  material 
system  is  attended  by  effects  retardative  to  the  transfer 
and  conducive  to  dissipation,  the  transfer  of  energy  into 
any  animate  material  system  is  attended  by  effects  con- 
ducive to  the  transfer  and  retardative  of  dissipation  '. 

Charging  a  Leyden  jar  or  heating  a  bar  of  iron  is  attended 
by  effects  very  different  from  those  which  attend  the 
feeding  of  an  animal. 

But  without  dwelling  on  this  technical  difference,  though 
it  seems  to  us  far-reaching,  we  may  emphasize  the  fact  that 
the  efficiency  of  the  living  creature  considered  as  an  engine 


THE  WONDER  OF  LIFE  473 

is  surprisingly  greater  than  that  of  our  best  engines.  A 
steam-engine,  for  the  most  part  made  of  iron,  is  a  material 
system  for  transforming  the  potential  energy  of  coal  into 
heat  and  work.  A  living  organism,  in  great  part  built  up 
of  proteids,  carbohydrates,  and  other  carbon- compounds, 
is  also  a  material  system  for  transforming  the  potential 
energy  of  food  into  heat  and  work.  But  the  living  organism, 
considered  as  an  engine,  is  much  more  effective  than  the 
locomotive.  For  while  the  best  steam-engine  turns  only 
about  twelve  per  cent,  of  its  income  of  potential  energy 
into  work ;  the  animal  can  give  back  as  much  as  twenty- 
five  per  cent.  Moreover,  the  actual  waste  of  heat  in  the 
steam-engine  is  much  greater  than  in  the  animal. 

We  need  not  elaborate  the  contrast  between  living 
creatures  and  engines.  To  any  one  bent  on  maintaining 
that  organisms  are  engines,  we  would  point  out  that  they 
are  self -stoking,  self -repairing,  self -regulating,  self-adjust- 
ing, self-resting,  self-increasing,  and  self-reproducing 
engines  ! 

In  his  interesting  book,  The  Cell  as  the  Unit  of  Life, 
Dr.  Allen  Macfadyen  wrote  : — 

'  A  great  part  of  physiological  inquiry  has  consisted 
in  the  examination  and  explanation,  not  of  life  but  of  the 
mechanism  of  life,  and  so  far  as  this  mechanism  is  con- 
cerned, adequate  and  satisfactory  explanations  have  been 
found  in  the  ordinary  laws  of  physics.  It  is  when  we  come 
to  cellular  activities  that  our  real  difficulties  begin  as  regards 
the  essentially  vital  problems '. 

It  is  interesting  to  look  up  the  works  of  Professor  W. 
Koux,  a  hard-headed  anatomist  and  embryologist,  the 
pioneer  in  the  modern  study  of '  developmental  mechanics  ', 
to  notice  how  constantly,  in  spite  of  that  word '  mechanics,' 


474  THE  WONDER  OF  LIFE 

which  he  uses  in  a  wide  sense,  he  refers  to '  self-preserva- 
tion ', '  self-increase  ',  '  self-adjustment ',  '  self -differentia- 
tion ',  '  self-regulation  ',  and  so  on. 

Another  note  may  be  useful  at  this  stage,  that  an  engine 
or  a  machine  is  not  exactly  a  fair  example  of  the  inanimate 
world.  It  is  a  sort  of  non- protoplasmic  extension  of  man's 
hand.  It  is  a  human  invention.  One  of  the  famous 
automata  had  a  clever  dwarf  shut  up  inside,  and  in  a  way 
there  is  a  human  idea  inside  every  machine.  This  makes 
a  difference. 

The  Insignia  of  Life. — What  are  the  radical  differences 
between  a  bird  and  the  stone  that  kills  it,  between  a  tree 
and  the  snow- crystals  that  transfigure  it  ?  What  does 
livingness  really  mean  ?  As  the  innermost  secret  of  life 
eludes  us,  this  section  of  the  chapter  might  end  with 
the  mark  of  interrogation.  On  the  other  hand,  while  we 
do  not  understand  what  the  essence  of  life  is,  it  may  not 
be  unprofitable  to  treat  living  creatures  descriptively, 
asking  ourselves  how  they  differ  from  not-living  things. 

Many  have  tried  to  state  in  a  few  words  the  characteristics 
of  living  organisms,  but  no  formulation  has  won  general 
acceptance.     The  best  we  know  is  given  by  Roux,  who 
recognizes  five  '  elementary  functions  ' : — 
I.  Self-disassimilation. 

II.  Self-preservation,    including    assimilation,    growth, 

movement,  feeding,  etc. 

III.  Self-multiplication. 

IV.  Self-development. 

V.  Self-regulation  in  the  exercise  of  all  functions,  in- 
cluding self-differentiation,  self-adjustment,  self- 
adaptation,  and  in  many  organisms  distinctly 
recognizable  psychical  functions. 


THE  WONDER  OF  LIFE  475 

Altogether,  according  to  Roux,  there  are  thirteen  general 
characters  of  living  creatures,  and  we  do  not  know  of  any 
that  he  has  omitted.  Yet  we  venture  to  arrange  the  char- 
acteristics somewhat  differently. 

Down-breaking  and  Up-building. — Every  normal 
organism  is  like  a  whirlpool  in  the  river,  always  changing 
and  yet  more  or  less  remaining  the  same.  It  is  like  the 
sunlit  top  of  a  fountain  rising  in  the  air  ;  its  component 
elements  are  restlessly  changing  on  their  way  up  or  on 
their  way  down.  Like  a  clock  it  is  always  running  down 
and  always  needing  to  be  wound  up ;  but  unlike  a  clock 
it  can  wind  itself  up.  Not  indefinitely,  indeed,  but  some 
of  the  Calif ornian  Big  Trees  (Sequoia  gigantea)  did  it,  as  we 
have  seen,  for  two  thousand  years — genuine  Methuselahs  ! 
The  constructive,  synthetic,  up-building  or  winding- 
up  processes  are  summed  up  in  the  term  Andbolism; 
the  destructive,  analytic,  down-breaking,  running-down 
processes  are  summed  up  in  the  term  Katabolism,  and  both 
are  included  in  a  term  that  covers  both,  Metabolism,  for 
which  we  have,  unfortunately,  no  English  equivalent — no 
word  like  the  fine  German  word  '  Stoffwechsel ',  change  of 
stuff.  Chemical  change  is  universal,  of  course,  but  the 
peculiarity  in  the  case  of  organisms  is  the  balancing  of 
accounts,  the  correlation  of  up-building  with  down-break- 
ing, of  the  winding-up  with  the  running-down.  That  is 
the  criterion  of  vital  processes,  biologically  considered, 
that  they  go  on  of  themselves,  that  they  form  part  of  a 
concatenated  series  of  chemical  processes  somehow  bound 
into  unity,  a  series  in  which  the  pluses  balance  the  minuses, 
and  the  thing  goes  on.  It  is  idle  to  try  to  express  it  in 
terms  of  what  goes  on  in  the  sterilized  chemical  laboratory, 
for,  taken  as  a  whole,  it  is  something  more.  Isolate  any 


476  THE  WONDER  OF  LIFE 

particular  reaction,  and  it  is  the  same  in  the  eagle  as  in  the 
test-tube ;  but  the  riddle  of  life  is  that  of  the  burning 
bush — nee  tamen  consumebatur. 

The  Power  of  Growing. — Given  a  material  system 
that  could  balance  accounts,  that  did  not  simply  run  down 
brilliantly  and  fizzle  out,  like  the  flaring  pill  of  potassium 
thrown  on  the  basin  of  water,  the  logically  second  criterion 
is  growth  or  self-increase.  A  surplus  of  income  over 
expenditure,  that  is  the  primal  condition  of  organic  growth 
(for  crystal  growth  and  osmotic  growth  is  not  relevant  at 
all)  ;  the  essential  criterion  is  that  out  of  material  quite 
different  from  itself  the  living  creature  is  able  to  meet  not 
only  current  expenditure,  but  to  lay  by  something — for 
growth.  That  income  should  exceed  expenditure  is  the 
obvious  condition  of  organic  growth. 

The  Capacity  for  Behaviour. — The  growth  of  an 
organism  implies  an  active  assimilation,  not  a  passive 
accretion,  but  it  makes  more  venturesome  activity  possible. 
Having  some  reserves  in  hand  is  one  of  the  conditions  of 
agency.  In  some  of  the  simplest  organisms  it  has  been 
observed  that  movement  stops  when  certain  substances 
included  in  the  living  matter  are  used  up,  and  does  not  begin 
again  until  they  are  replaced.  They  are  among  the  con- 
ditions of  behaviour,  just  as  food  and  water  are  among  the 
conditions  of  the  continued  progress  of  a  band  of  explorers. 
But  the  life  is  more  than  meat. 

When  we  study  the  activities  of  the  very  simplest 
organisms  we  do  not  find  that  they  are  simple.  The  move- 
ments of  advance  and  retreat  and  re-advance  exhibited 
by  some  of  the  mysterious  slime-fungi  (Myxomycetes)  are 
beyond  any  re-description  in  terms  of  present-day  chemis- 
try and  physics.  They  exhibit  the  rudiments  of  behaviour. 


THE  WONDER  OF  LIFE  477 

The  flowing  movements  of  an  amoeba  cannot  be  inter- 
preted as  a  result  of  local  changes  in  surface  tension,  or  the 
like.  Though  surface  tension  phenomena  are  involved, 
the  movement  is  self-determined.  Professor  Jennings  has 
described  the  behaviour  of  an  amoeba  which  pursued  a 
spherical  cyst  of  Euglena  for  fifteen  minutes.  One  amoeba 
pursued  another  for  a  long  time,  finally  capturing  and 
ingesting  it.  But  after  being  carried  for  a  short  distance, 
the  prey  partly  escaped  and  was  recaptured.  It  again 
escaped,  this  time  completely,  but  was  pursued,  overtaken, 
recaptured,  and  again  carried  away.  After  five  minutes 
it  escaped  again,  this  time  completely  and  successfully, 
so  that  the  hunter  amoeba  did  not  have  its  meal  after  all. 
But  this  is  more  than  surface  tension. 

It  seems  to  be  one  of  the  insignia  of  life  that  the  organism 
registers  within  itself  the  results  of  its  experiences.  As 
Professor  W.  K.  Clifford  said  :  '  It  is  the  peculiarity  of 
living  things  not  merely  that  they  change  under  the 
influence  of  surrounding  circumstances,  but  that  any  change 
which  takes  place  in  them  is  not  lost,  but  retained,  and 
as  it  were  built  into  the  organism  to  serve  as  the  foundation 
for  future  actions  '.  As  Professor  Henri  Bergson  puts  it : 
*  Its  past,  in  its  entirety,  is  prolonged  into  its  present,  and 
abides  there,  actual  and  acting '. 

To  begin  with,  there  must  be  a  viable  balance  of  up- 
building and  down-breaking — the  essential  modus  vivendi  ; 
then  there  must  be  addition  to  the  specific  structure,  so 
that  some  rest  is  possible  in  one  part  while  another  is 
working  hard  ;  along  with  that  will  go  the  accumulation 
of  some  capital,  so  that  the  organism  is  not  always  living 
from  hand  to  mouth ;  this  makes  more  energetic  action 
possible,  and  more  thorough  re-creation  of  the  specific 


478  THE  WONDER  OF  LIFE 

structure.  Thus  we  may  begin  to  think  of  the  conditions 
of  agency,  of  experimenting,  of  trafficking  with  time,  and 
of  multiplying. 

Power  of  Reproducing. — Growth  is  self -increase,  and 
it  leads  on  to  reproduction  which  is  self-multiplication. 
In  a  simple  organism — a  nucleated  corpuscle  of  living 
matter — growth  proceeds  up  to  a  certain  point  which 
we  call  the  limit  of  growth.  Beyond  that  it  is  dangerous 
for  the  corpuscle  to  grow,  unless  indeed  it  secures  at  the 
same  time  great  increase  of  surface.  We  have  already 
referred  (p.  396)  to  what  was  pointed  out  by  Herbert 
Spencer  and  others,  that  if  the  corpuscle  be  a  sphere,  as  it 
often  is,  the  volume  (whose  contents  have  to  be  kept  alive) 
increases  as  the  cube  of  the  radius,  whereas  the  surface 
(through  which  the  keeping  alive  is  effected)  increases 
only  as  the  square.  Thus  if  it  grow  beyond  a  certain  size, 
the  corpuscle  gets  into  difficulties.  There  is  also  an 
optimum  ratio  between  the  nucleus  and  the  rest  of  the 
cell-substance. 

Development. — We  are  trying  to  see  the  essential 
criteria  of  life  in  a  logical  order.  The  power  of  sustained 
metabolism — of  balancing  accounts — makes  activity  and 
growth  possible  ;  growth  naturally  leads  on  to  multiplica- 
tion ;  and  the  power  of  development  that  an  isolated  frag- 
ment, or  sample,  or,  it  may  be,  germ-cell  possesses  of  re- 
expressing  the  whole  is  surely  a  continuation  of  the  restitu- 
tion and  regrowth  which  goes  on  to  make  good  the  body's 
wear  and  tear,  and  of  the  regeneration  which  is  exhibited 
when  a  lost  part  is  replaced.  Development  is  the  making 
visible  of  the  latent  manifoldness  of  the  liberated  fragment, 
or  sample,  or  cell.  It  is  the  expression  of  latent  possi- 
bilities— it  is,  subjectively  regarded,  a  kind  of  self-expres- 


THE  WONDER  OF  LIFE  479 

sion.  Out  of  the  apparently  simple  there  arises  the  obvi- 
ously complex,  as  the  chicken  is  '  coined  and  minted  out 
of  the  egg  '.  There  are  the  two  great  processes  : — differen- 
tiation (which  is  the  structural  side  of  division  of  labour), 
and  integration  (which  means  the  unification  and  har- 
monization and  controlling  of  all  the  parts).  The  develop- 
ing creature  becomes  more  visibly  complex  ;  it  also  becomes 
knit  together  as  a  unity.  Development  always  implies 
these  two  processes. 

Variability. — It  is  well  known  that  some  of  the  simplest 
organisms — which  remain  single  cells — occur  in  different 
forms  and  with  different  qualities  in  different  circumstances. 
Thus  the  same  Bacterium  may  be  virulent  or  relatively 
attenuated  in  its  poisoning  capacity,  and  '  polymorphic  ' 
Protozoa,  e.g.  some  Trypanosomes,  are  described.  It  does 
not  seem  that  these  diversities  are  simply  individually 
acquired  peculiarities,  due  to  some  peculiarity  in  the  parti- 
cular environment.  They  may  have  arisen  in  some  such 
way,  but  they  often  appear  to  have  taken  grip  of  the  con- 
stitution ;  they  are  not  individual,  but  racial  peculiarities, 
and  will  persist  for  a  while  even  when  the  environment  is 
altered. 

This  variability  of  the  living  organism  is  characteristic 
and  fundamental.  It  has  to  be  accepted,  at  present,  as  a 
primary  fact  of  life,  but  some  suggestions  may  be  considered 
which  tend  to  leave  it  less  apart.  In  the  inanimate  world 
there  is  a  tendency  in  matter  to  complexify,  for  atoms  to 
build  up  molecules,  and  molecules  larger  molecules,  and  so 
on.  There  is  also  a  certain  variability  in  the  crystallization 
of  one  and  the  same  chemical  substance,  which  may  appear 
in  several  different  forms.  Every  one  has  looked  at  the 
beautiful  diversity  among  snow-flakes.  Now  it  may  be 


480  THE  WONDER  OF  LIFE 

that  the  tendency  to  complexify  that  is  seen  in  things 
inanimate  is  carried  on  into  organisms,  and  finds  expression 
in  variation. 

There  are  many  peculiarities  in  the  bodies  of  higher 
animals  which  are  certainly  not  the  direct  results  of  some 
peculiarity  in  the  environment,  but  are,  we  believe,  the 
expression  of  variations  in  the  germinal  substance.  Yet  it 
has  to  be  remembered  in  regard  to  these  variations  that  the 
environmental  peculiarities  may  have  served  to  prompt 
the  germ- cells  to  some  internal  re-arrangement  of  their 
organization. 

Weismann  has  laid  emphasis  on  the  fact  that  the  ger- 
minal substance  in  the  germ-cells  is  subjected  to  the  changes 
and  fluctuations  in  the  nutritive  stream,  and  it  is  possible 
that  these  may  serve  to  prompt  germinal  variations.  He 
has  also  suggested  that  there  may  be  within  the  germ-cell 
a  literal  struggle  among  the  hereditary  items  or  factors, 
just  as  there  is  a  struggle  among  the  different  parts  of  the 
body. 

Another  consideration  is  this,  that  in  the  ripening  of  the 
egg-cell  there  appears  to  be  an  opportunity  for  the  dropping 
out  of  hereditary  items,  and  as  a  matter  of  fact  we  know 
that  items  are  very  often  dropped  out.  In  albinos  a  pig- 
ment-producing or  pigment-completing  factor  is  dropped 
out.  Moreover,  in  fertilization,  as  we  have  seen,  there  are 
opportunities  for  new  permutations  and  combinations, 
when  the  paternal  and  maternal  contributions  enter  into 
intimate  and  orderly  union.  Two  sex-cells  become  one — 
a  unified  individual,  not  merely  an  inheritance-packed  cell. 
In  the  compromise  effected  between  similar  items,  in  the 
unified  organization  arrived  at,  there  is  probably  many  an 
opportunity  for  something  new. 


THE  WONDER  OF  LIFE  481 

Simulacra  Vitae. — Biitschli,  following  Quincke,  showed 
how  mimic  cells  might  be  produced  by  putting  drops  of 
fine  emulsions  in  suitable  media.  Some  old  olive  oil  beaten 
up  with  a  little  powdered  potassium  carbonate  forms  a 
very  fine  emulsion — an  acid  in  the  oil  attacking  the  salt 
and  liberating  microscopic  vacuoles  of  carbon  dioxide. 
The  resulting  emulsion  is  a  microscopic  foam,  and  micro- 
photographs  of  drops  of  it  look  like  micro-photographs 
of  some  kinds  of  cells.  For  a  time  this  resemblance  gave 
corroboration  to  the  view  that  the  minute  structure  of 
cell-substance  or  cytoplasm  was  of  the  nature  of  a  very 
fine  foam  or  emulsion,  though  of  course  made  of  very  much 
more  complex  materials  than  olive  oil.  It  cannot  be  said, 
however,  that  recent  histological  research  has  given  support 
to  this  interpretation. 

It  is  doubtful  whether  these  simulacra  vitse  throw  much 
light  on  the  structure  and  activity  of  living  cells,  though 
it  is  quite  probable  that  they  may  have  a  bearing  on  the 
formation  of  non-living  bodies  made  by  organisms,  such 
as  shells  and  pearls,  spicules  and  calcareous  corpuscles. 
If  a  weak  solution  of  gelatine  is  spread  on  a  slide  and  tiny 
drops  of  ferrocyanide  of  potassium  are  put  on  at  intervals 
of  five  millimetres  or  so,  the  result  is  the  production  of 
rather  striking  simulacra  of  nucleated  cells.  But  do  these 
simulacra  in  relatively  simple  material  throw  much  light 
on  the  structure  of  vital  units  ?  They  are  as  remote  as 
concentrically  laminated  agates  are  from  tree-stems,  as 
remote  as  the  beautiful  dendritic  growths  of  manganese 
dioxide  are  from  zoophytes. 

Professor  Stephane  Leduc  has  given  much  time  to  the 
study  of  wonderful  inorganic  growths  which  he  is  able  to 
induce,  and  they  certainly  show  what  complex  and  beauti- 

J  l 


482  THE  WONDER  OF  LIFE 

ful  structures  may  arise  in  relatively  simple  media.  Thus  if 
fragments  of  calcium  chloride  be  dropped  into  a  litre  of  dis- 
tilled water  containing  sixty  grains  of  silicate  of  potassium, 
sixty  grains  of  saturated  solution  of  carbonate  of  soda, 
and  thirty  grains  of  saturated  dibasic  phosphate  of  soda, 
then  beautiful  phantasms  arise — '  osmotic  growths  ' — like 
mushrooms  and  moulds  and  corals  and  shells.  They 
show  us  the  possibilities  of  inorganic  growth,  and  perhaps 
they  may  be  of  service  in  bringing  into  stronger  relief  what 
is  distinctive  in  organic  growth.  They  may  be  of  use 
for  comparison  with  osmotic  phenomena  in  organisms, 
but  we  are  unable  to  see  that  they  throw  much  light  on  the 
essential  nature  of  growth  in  organisms.  It  appears  to  us 
to  be  giving  an  entirely  false  simplicity  to  the  facts  to 
suggest  that  Biology  is  a  subdivision  of  the  physico- 
chemistry  of  fluids.  This  is  a  survival  of  the  uncritical 
materialistic  superstition,  and  to  credit  the  artificial 
osmotic  growths  with  nutrition,  assimilation,  irritability, 
and  a  power  of  development  is  a  bad  instance  of  an  asser- 
tion that  outstrips  its  evidence. 

Difficult  Phenomena. — However  much  more  it  may 
be,  living  certainly  is  the  correlation  of  a  series  of  physical 
and  chemical  processes  that  go  on  within  the  organism.  But 
it  is  impossible  to  ignore  a  thicket  of  difficulties.  Even  after 
the  organization  has  been  fatally  shattered,  parts  of  the  body 
may  continue  active.  A  wasp,  indeed,  may  continue  sucking 
syrup  though  some  tough  friend  of  the  public  comfort  has 
cut  right  through  its  waist.  On  the  other  hand,  it  is  not 
easy  to  find  evidence  of  activity  in  the  hibernating  snail, 
or  in  the  resting  pupae  of  some  insects,  and  yet  life  has  not 
sped.  There  is  nothing  in  either  case  by  which  we  could 
very  readily  prove  to  the  sceptical  that  death  had  not 


THE   WONDER  OF   LIFE  483 

occurred,  though  microscopic  examination  would  show 
that  some  of  the  cells  were  alive.  But  how  much  more 
difficult  the  question  becomes  when  we  pass  to  dried  up 
paste-eels,  small  thread- worms  or  Nematodes  of  the  family 
Anguillulidse,  which  can  remain  dry  and  brittle  for  as 
long  as  fourteen  years,  and  yet  become  lively  again  when 
restored  to  water !  What  is  life  in  these  inert  threads, 
which  exhibit  no  sign  of  living  ?  What  has  happened  in 
the  fifteenth  year,  when  although  no  visible  change  has 
occurred,  the  threads  are  no  longer  susceptible  to  the 
reviving  influence  of  water  ?  They  are  dead  ;  but  what 
has  happened  ? 

Latent  Life. — The  familiar  sight  of  bags  of  dry  seeds 
in  the  seedsman's  shop  raises  many  questions.  In  what 
state  is  the  life  of  these  seeds — for  it  is  to  be  hoped  that 
most  of  them  are  still  alive  ?  Can  they  remain  alive 
without  actually  living  ?  Vital  processes  involve  chemical 
change  (metabolism)  :  has  metabolism  come  to  a  stand- 
still or  is  it  going  on  very  slowly  ?  It  is  not  so  easy  to  test 
this  as  might  be  imagined,  for  the  fire  of  life  may  be  kept 
burning  so  very,  very  low  that  no  change  is  detectable  in 
the  surrounding  medium.  Some  plants  can  respire  without 
taking  in  oxygen  from  outside,  and  some  others,  e.g. 
succulents,  can  respire  without  giving  out  any  carbon 
dioxide.  Of  course  if  the  protoplasm  is  actually  living  it 
is  transforming  energy,  and  if  it  has  no  income  it  must  be 
living  on  its  own  resources,  therefore  the  life  of  seeds  must 
be  limited.  We  know  securely  from  Becquerel's  careful 
testing  that  seeds  may  germinate  after  resting  for  eighty- 
seven  years  in  a  herbarium — a  hortus  siccus  indeed. 

Becquerel  has  made  important  experiments  on  the 
latent  life  of  dry  seeds.  He  showed,  for  instance,  that  the 


484  THE  WONDER  OF  LIFE 

dry  seed-coats  of  peas  and  beans,  and  of  many  others  which 
can  germinate  after  prolonged  desiccation,  are  air-proof. 
When  detached  pieces  were  fitted  on  to  the  top  of  a  tube 
of  mercury,  above  a  Torricellian  vacuum,  no  air  was 
drawn  through — even  in  months.  Thus  a  dry  seed  is 
peculiarly  isolated.  When  the  coats  are  wet,  the  absorp- 
tion of  water  changes  the  situation,  and  gaseous  exchange 
begins. 

Becquerel's  later  experiments  are  very  striking.  He  took 
seeds  of  wheat,  mustard,  and  lucerne,  and  perforated  their 
coats ;  dried  them  in  a  vacuum  at  40°  C.  for  six  months ; 
sealed  them  up  in  an  almost  exhausted  tube  for  a  year ; 
submitted  them  to  the  temperature  of  liquid  air  (  —  190°) 
for  three  weeks,  and  of  liquid  hydrogen  (—250°)  for  three 
days  ;  and  then  put  them  on  moist  cotton  wool — and  they 
germinated  as  usual !  In  a  review,  Prof.  Cavers  gives 
a  terse  statement  of  Becquerel's  conclusion.  '  Bec- 
querel  finds  it  impossible  to  conceive  of  "  life  "  under  the 
conditions  to  which  these  seeds  were  subjected,  and  holds 
that  life  can  be  interrupted  completely — not  merely  slowed 
down — with  no  prejudice  to  its  resumption '. 

Various  fungoid  organisms  have  been  known  to  survive 
twenty- two  years'  desiccation;  various  bacteria  have 
remained  alive  without  air  but  with  moisture  for  ten  to 
twenty  years ;  sediments  containing  various  Protozoa 
have  shown  re-vivification  after  five  to  six  years.  J.  Noc 
relates  that  some  tubes  with  a  little  water  and  various 
Protozoa  were  hermetically  sealed  in  1908,  and  were 
recently  examined.  There  was  no  trace  of  the  Infusorians 
which  were  there  to  start  with,  but  there  were  encysted 
Amoebae,  some  of  which  revived  after  ten  days  or  so. 
Some  Protozoa  dried  on  Tonkin  commercial  paper  were 


THE  WONDER  OF  LIFE  485 

revived  after  five  years.  One  of  these  was  a  small  Flagel- 
late, Oikomonas  termo. 

Local  Life. — The  phenomena  of  local  life  demand  care- 
ful consideration.  On  the  one  hand,  we  have  many  cases 
of  fragments  which  grow  into  wholes.  On  the  other  hand, 
we  have  curious  examples  of  parts  which  can  live  on  for  a 
long  time  after  the  whole  has  been  destroyed,  though  they 
show  little  or  no  power  of  regeneration.  Let  us  illustrate 
the  first  set  of  cases  first.  Every  one  knows  that  a  piece 
of  a  branch  or  a  piece  of  a  potato  will  remain  alive  for  a  con- 
siderable time  after  being  cut  off,  and  will  in  appropriate 
conditions  grow  into  a  complete  plant.  Posts  of  wood, 
believed  toJbe  dead,  sometimes  burst  into  leaf  after  they  have 
been  driven  into  the  ground.  A  small  fragment  of  many  a 
plant,  from  Liverwort  to  Begonia,  will  grow  into  a  complete 
plant.  And  similarly,  a  fragment  of  sponge,  of  hydroid,  of 
sea-anemone,  of  certain  worms,  and  so  forth,  can  regrow  the 
whole.  There  is  need  of  precise  experiment  to  determine 
the  limits  and  conditions  of  these  regenerations  of  wholes 
from  parts.  In  the  case  of  Hydra,  it  has  been  found  that 
the  regenerating  fragment  must  not  be  too  small — a  quanti- 
tative limit,  and  that  it  must  contain  samples  of  the 
different  kinds  of  cells  in  the  body — a  qualitative  limit. 
A  tentacle  will  not  regrow  a  polyp,  though  a  polyp  soon 
regrows  a  tentacle.  Very  extraordinary  are  the  recent 
experiments  of  Professor  H.  V.  Wilson  which  show  that 
some  sponges  may  be  minced  up  and  strained  through  a 
cloth  strainer — and  yet  the  debris  poured  out  in  an  appro- 
priate place  will  develop  into  a  proper  sponge.  It  is  a 
verification  of  one  of  the  old  myths — of  Zagreon,  who 
was  cut  into  pieces  and  yet  survived. 

As  to  the  second  set  of  cases,  where  parts  live  on  though 


486  THE  WONDER  OF  LIFE 

without  regenerative  power  or  only  a  little  of  it,  we  may 
recall  the  familiar  case  of  the  turtle's  heart,  which,  in 
appropriate  conditions,  will  continue  beating  for  several 
days  after  the  bulk  of  the  animal  has  been  made  into  soup, 
and  has  passed  into  a  new  incarnation.  There  it  goes  on 
beating  in  its  warm  and  humid  glass  case — a  fine  illustra- 
tion of  local  life. 

Of  recent  years  very  remarkable  experiments  have  been 
made  in  keeping  pieces  of  tissue  alive  in  suitable  media 
outside  the  body.  What  happens  in  most  cases  is  that  they 
live  on  for  a  time,  grow  a  little,  and  die.  Perhaps  we  should 
know  a  good  deal  if  we  understood  why  they  die.  It  has 
been  suggested  that  the  death  may  be  contingent  rather 
than  necessary,  that  it  may  be  due,  for  instance,  to  the 
accumulation  of  waste  products.  With  this  idea  in  mind, 
Alexis  Carrel  has  devised  a  system  of  artificial  rejuven- 
escence, washing  the  piece  of  tissue  from  time  to  time  in 
'  Ringer's  solution ',  and  placing  it  in  a  medium  of  plasma 
and  distilled  water.  A  piece  of  connective  tissue  revived 
nine  times  after  this  bathing  treatment — staving  off  senes- 
cence and  death  for  more  than  a  month  after  its  removal 
from  the  body. 

Every  one  knows  that  egg-cells  can  remain  for  a  long 
time  alive  but  without  developing.  Much  more  remarkable 
is  the  fact  that  spermatozoa  can  be  kept  alive  in  a  salt 
solution  for  a  week.  Very  much  more  remarkable  is  the 
fact  that  isolated  red  blood  corpuscles,  of  the  newt  for 
instance,  can  be  kept  alive  for  a  fortnight.  Jolly  took  a 
small  quantity  of  blood  directly  from  the  newt's  heart, 
put  it  in  a  tube  placed  in  ice,  and  found  the  white  blood 
corpuscles  alive  after  4|  months.  Verily  the  tenacity  of 
life  is  great. 


THE  WONDER  OF  LIFE  487 

Powers  of  Life. — Life  is  a  powerful  kind  of  activity. 
We  see  this  in  many  ways — in  the  power  of  self-increase 
that  is  so  characteristic  of  living  matter,  one  Infusorian 
becoming  a  million  in  a  week ;  in  the  associated  power 
of  transforming  matter,  the  green  plant  changing  air, 
water,  and  salts  into  bread,  the  animal  changing  the  plant 
into  flesh  ;  in  the  economical  transformations  of  energy, 
for  as  we  have  already  mentioned,  an  organism  considered 
as  an  engine  gives  more  return  for  the  potential  energy 
supplied  to  it  (the  food  or  fuel)  than  any  engine  of  man's 
device  ;  in  the  capacity  for  storing  potential  energy  without 
much  leakage,  as  we  see  so  convincingly  in  the  trees  of 
the  forest ;  in  the  manifoldness  of  the  energy-transform- 
ations that  are  accomplished,  for  we  find  one  and  the  same 
creature  doing  work,  giving  off  heat,  giving  off  light,  and 
exhibiting  electrical  changes  ;  in  the  exquisite  responsive- 
ness, for  a  sundew  tentacle  will  detect  the  presence  of  a 
minute  drop  of  ammonium  carbonate  added  to  a  large  jar 
of  water,  and  the  earthworm,  though  without  ears,  is  aware 
of  the  light  tread  of  a  thrush's  foot.  As  it  is  impossible 
to  discuss  all  the  powers  of  life,  our  method  must  be,  as 
throughout,  only  illustrative.  We  shall  discuss  two 
powers  or  capacities  as  different  as  possible — the  power  of 
giving  forth  light,  and  the  power  of  taking  a  rest  in  sleep. 

Luminescence. — In  illustration  of  the  powers  of  life, 
let  us  take  the  phenomenon  of  luminescence,  or,  as  it  has 
been  erroneously  called,  phosphorescence.  From  the 
chemico-physical  point  of  view,  the  organism  is  a  material 
system  which  effects  the  transformation  of  matter  and 
energy.  It  is  the  seat  of  continuous  chemical  changes — 
oxidations  and  reductions,  hydrations  and  fermentations — 
which  we  sum  up  in  the  term  metabolism.  There  is  no 


488 


THE  WONDER  OF  LIFE 


doubt  that  the  production  of  light  is  one  of  the  results  of 
this  metabolism.  Just  as  heat  is  produced  by  the  vital 
activity  of  the  muscles  (their  characteristic  '  thermogenic  ' 
function)  and  by  all  the  combustions  that  go  on  in  the 
body,  so  light  is  produced  in  connexion  with  other  chemical 
processes  involved  in  living.  Many  facts  point  to  the  con- 


CHB- 


FIG.  78. — Phosphorescent  cell.  (After  Watase.)  c,  Cytoplasm  of  the 
cell ;  CHB,  Chromosomes  of  the  nucleus — living  constituents. 
A,  Food ;  PH,  Photogenic  Granules — not  living  constituents. 
Oxygen  acts  on  the  photogenic  granules,  and  Light  emanates 
from  the  cell  as  the  result  of  oxidation. 


elusion  that  the  luminescence  need  not  be  in  itself  of  any 
biological  importance,  any  more  than  the  heat  produced 
in  the  active  brain  is  normally  of  any  importance,  any 
more  than  the  beautiful  colour  of  some  organic  waste 
products  is  in  itself  of  any  importance.  But  just  as  the 
production  of  heat  or  of  pigment  may  be  turned  to  good 


THE  WONDER  OF  LIFE  489 

account  and  made  vitally  important,  so  it  may  be  with 
the  production  of  light. 

The  facts  in  regard  to  luminescence  in  organisms  raise 
many  unanswered  questions  and  demand  further  investiga- 
tion, but  there  is  no  particular  difficulty  about  the  bare 
fact  that  light  is  produced  in  laboratories  which  give  off 
heat,  as  we  all  experience,  and  generate  electricity,  as  we 
may  experience  on  close  acquaintance  with  the  Electric 
Eel  or  the  Torpedo. 

A  noteworthy  fact  in  regard  to  luminescence  is  its  wide 
distribution  in  the  sea.  When  the  oars  drip  sparks  on  a 
summer  night  we  see  the  luminescence  of  Noctiluca  ;  and 
there  are  many  pelagic  animals — some  Radiolarians,  some 
Medusae,  most  Ctenophores,  some  '  worms  ',  many  crus- 
taceans, a  few  molluscs,  Tunicates  like  the  splendid  Pyro- 
soma,  and  various  surface  fishes — which  are  luminescent. 
In  the  shore  area  there  are  luminescent  Echinoderms, 
especially  Brittle-stars ;  the  boring  Pholads — with  their 
miners'  lamps  ;  and  various  members  of  the  great  alliance 
of  Stinging  Animals  or  Ccelenterates.  In  the  great  abysses, 
as  we  have  noticed,  luminescence  is  common,  e.g.  among 
Alcyonarians,  Medusae,  Echinoderms,  Crustaceans,  Cuttle- 
fishes, and  true  fishes.  On  land  we  know  it  best  in  glow- 
worms, fire-flies,  and  other  insects,  but  it  also  occurs  in 
some  Myriopods  (e.g.  Geophilus  electricus),  and  in  some 
earthworms  (e.g.  Photodrilus).  It  is  usually  said  to  be 
quite  absent  in  freshwater  animals,  but  we  have  some 
suspicions  as  to  the  accuracy  of  this  generalization,  bearing 
in  mind  Nelson  Annandale's  freshwater  Lampyrid  and 
allegations  of  luminescent  Chironomid  larvae.  That  there 
are  phosphorescent  Bacteria  is  well  known — every  one  can 
see  them  on  fish  hung  up  to  dry — and  it  is  probable  that 


490  THE  WONDER  OF  LIFE 

reports  of  luminous  birds  are  due  to  luminescent  fungi 
on  the  plumage. 

In  a  case  like  trie  luminescence  of  Bacteria,  no  one  even 
looks  for  a  utilitarian  explanation.  The  luminescence  is  a 
by-play  of  vitality  ;  it  is  one  of  the  residual  powers  of  the 
organism  ;  and  it  is  probably  exhibited  in  many  cases  in 
which  we  do  not  and  cannot  see  it.  What  we  need  to  know 
is  (1)  the  internal  physiology  of  luminescence,  and  (2) 
what  its  use  may  be  in  certain  cases  where  it  bears  the  marks 
of  specialization. 

The  luminescence  is  in  some  cases  indissolubly  connected 
with  the  cellular  metabolism — as  in  Noctiluca,  Brittle-stars, 
and  some  fishes.  When  they  die  their  light  goes  out. 
In  other  cases  the  luminescent  material  is  not  luminescent 
until  it  is  exuded  from  its  producer  into  the  water,  as  in 
many  Copepods.  The  light  does  not  require  contact  with 
life  to  keep  it  shining.  The  trail  of  the  luminous  Myriopod 
is  luminous,  and  in  some  cases  (Copepods,  Lampyrids, 
and  Pholads)  the  luminous  secretion  can  be  dried  and 
yet  retain  its  capacity  of  giving  forth  light  when  it  is  put 
into  water  after  several  days,  weeks,  or  months. 

In  the  American  Lampyrid  beetles,  popularly  called  fire- 
flies, the  light-producing  organ,  as  described  by  McDermott 
and  Crane,  consists  of  two  layers.  The  inner  one,  white 
and  opaque,  seems  to  serve  as  a  reflector,  and  perhaps 
protects  the  insect  from  its  own  brightness.  The  outer 
one,  yellowish  and  translucent,  is  the  seat  of  the  actual 
photogenic  process.  It  is  interesting  to  know  that  innu- 
merable air-tubes  or  tracheae  penetrate  the  organ,  for 
this  bears  out  the  conclusion  otherwise  arrived  at,  that 
the  luminescence  is  due  to  an  oxidation. 

In  the  American  fire-fly  both  sexes  are  luminescent,  the 


THE   WONDER  OF   LIFE  491 

flightless  female  less  so  than  her  active  partner.  The 
luminescent  organs  of  the  male  consist  of  a  pair  of  plates, 
lying  beneath  the  skin  on  the  ventral  surface  of  the  fourth 
and  fifth  abdominal  segments.  Each  plate  has  two  layers, 
and  the  lower  is  built  up  of  polygonal  cells  filled  with 
coarse  granules.  In  this  lower  layer  there  is  probably  a 
rapid  oxidation  of  some  unstable  substance,  perhaps  of  a 
fatty  nature.  It  is  possible  that  the  decomposition  may 
be  accelerated  by  some  ferment.  Mrs.  A.  B.  Howard  has 
called  attention  to  the  fact  that  the  light  is  unaccompanied 
by  perceptible  heat.  It  is  therefore  produced  at  the  least 
possible  expenditure  of  energy,  as  Professor  Langley  long 
ago  pointed  out. 

In  fire-flies  of  the  genus  Luciola  the  light  given  off 
has  a  beautiful  green  fluorescence,  and  is  able,  like  X-rays, 
to  affect  a  photographic  plate  through  opaque  media,  such 
as  layers  of  wood  or  leather.  The  light  cannot  be  taken 
as  phosphorescent,  but  includes  rays  which  are,  at  least, 
'  similar  to  X-rays  and  ultra-violet  light  in  so  far  as  they 
render  certain  opaque  media  transparent,  and  are  inter- 
cepted by  glass '. 

In  an  interesting  study  on  the  luminous  organs  of  cuttle- 
fishes, Dr.  W.  E.  Hoyle  calls  attention  to  their  occurrence 
in  so  many  and  such  scattered  families,  that  repeated  and 
independent  origination  seems  probable.  They  are  almost 
always  on  the  ventral  surface  of  the  Cephalopod,  but  they 
occur  there  in  nine  different  situations.  Sometimes  they  are 
concealed  beneath  the  mantle  or  beneath  the  skin,  but 
they  may  be  effective  even  then,  since  the  living  tissues 
of  cuttlefishes  are  very  transparent.  It  is  plausible  to 
suppose  that  they  serve  as  recognition  marks,  and  that 
they  act  as  searchlights,  playing  over  the  floor  of  the  sea. 


492  THE  WONDER  OF  LIFE 

Some  of  them  are  simple,  but  others  have  a  complicated 
optical  apparatus  with  some  or  all  of  the  following  structures 
— pigment  layer,  reflector,  lens,  and  diaphragm.  While 
we  may  say  that  the  production  of  light  is  parallel  to  the 
production  of  heat  in  a  muscle  or  of  electric  discharges  in 
Torpedo,  there  must  be  some  definite  utility  when  the  organs 
have  a  complicated  apparatus.  Very  noteworthy  is  the 
remarkable  economy  of  the  illuminant ;  a  quite  infinites- 
imal proportion  of  the  energy  is  wasted  on  the  production 
of  heat. 

In  two  surface  fishes  of  the  Malay  Archipelago, 
Anomalops  katoptron  a,nd.Photoblepharon  palpebralis,  studied 
by  0.  Steche  (1909),  there  are  very  large  luminous  organs 
about  the  head,  which  seem  to  give  out  a  constant  light 
without  requiring  any  particular  stimulus.  The  lumin- 
escence has  its  seat  in  material  secreted  by  glandular  cells, 
and  occurs  outside  the  cells  in  the  cavity  of  the  gland  which 
they  form.  In  the  fishes  we  have  mentioned,  the  lumin- 
escent organ  can  be,  so  to  speak,  extinguished  by  a  down- 
ward movement,  which  possibly  takes  place  when  an  enemy 
appears  on  the  scene. 

Messrs.  Holt  and  Byrne  describe  a  remarkable  deep-water 
fish,  Lamprotoxus,  from  the  south-west  coast  of  Ireland. 
It  bore  a  filamentous  barbule  many  times  longer  than  the 
body.  The  colour  of  the  scaleless  skin  was  velvety- 
black  and  the  barbule  was  grey.  A  purplish-grey  cord-like 
band  of  luminous  tissue,  partially  embedded  in  the  skin, 
formed  a  closed  loop  on  the  anterior  part  of  the  body. 
There  was  also  a  large  photophore  behind  and  slightly 
below  the  eye,  occluded  by  skin  save  for  a  narrow  slit ; 
and  there  were  numerous  very  small  photophores. 

There  is  little  direct  evidence  as  to  the  use  of  luminescence, 


THE  WONDER  OF  LIFE 


493 


and,  as  we  have  said,  there  are  probably  many  cases  where 
it  is  of  no  use.  But  this  cannot  be  the  case  when  it  is 
associated  with  highly  specialized  organs.  And  when  we 
see  a  female  glow-worm  with  luminescent  organs  on  the 
under  side  of  the  body  turning  herself  back  downwards 
with  the  result,  at  any  rate,  that  her  light  is  visible,  we 
find  it  difficult  to  believe  that  the  light  is  not  attractive  to 


FIG.  79. — A  remarkable  fish,  Lamprotoxus  flagellibarba,  from  deep 
water  off  S.W.  of  Ireland.  The  small  spots  and  the  '  looped 
band  '  seem  to  be  luminous  organs.  The  barbel  is  many  times 
longer  than  the  body,  which  is  about  seven  inches  in  length.  (After 
Holt  and  Byrne.) 


the  male.  Many  animals  move  towards  a  light,  and  it  is  a 
very  probable  view  that  the  luminescence  of  many  marine 
animals  helps  to  bring  food  to  them.  Professor  Max  Weber 
mentions  the  very  interesting  fact  that  the  fishermen  of 
Banda  cut  out  the  luminous  organ  of  Anomalops  and  similar 
fishes,  and  use  it  as  a  bait,  for  it  keeps  on  shining  for  hours. 
A  sudden  illumination  of  a  luminous  organ,  or  a  sudden 
discharge  of  a  luminous  secretion  may  have  a  protective 


494  THE  WONDER  OF  LIFE 

value.  In  the  darkness  of  the  great  abysses  some  animals 
may  possibly  use  their  luminous  organs  as  lanterns.  Where 
the  luminous  organs  are  arranged  on  a  definite  pattern — 
which  is  sometimes  different  in  the  two  sexes — it  is  quite 
likely  that  they  serve  as  recognition  marks.  But  for  our 
present  purpose  it  is  enough  to  indicate  that  this  peculiar 
transformation  of  energy — not  in  itself  necessarily  useful — 
may  be  seized  upon,  utilized,  and  specialized  towards  diverse 
ends  by  different  types. 

Sleep. — It  appears  to  us  to  be  characteristic  of  the  life 
or  activity  of  organisms  that  it  can  be  slowed  down  and 
quickened  again.  We  may  hunt  out  analogies,  such  as 
that  of  a  fire  which,  after  vigorous  burning,  smoulders, 
and  then  breaks  out  again  ;  but  no  mere  mechanisms  have 
the  organism's  power  of  taking  a  rest,  and  one  of  the  many 
forms  of  rest  is  ordinary  sleep — that  familiar  but  puzzling 
state  in  which  we  spend  about  a  third  part  of  our  existence. 
Analogous  but  quite  different  vital  adjustments  are  to  be 
seen  in  the  hibernation  of  such  animals  as  snail  and  dor- 
mouse, and  in  the  so-called  '  sleep  '  of  plants  which  often 
makes  itself  plain  in  the  altered  position  of  the  leaves  and 
the  closing  of  the  flowers. 

Normally,  there  can  be  no  doubt,  the  sleeping  habit  was 
established  in  relation  to  sunset,  but  every  one  knows  that 
we  can  adjust  our  capacity  for  going  to  sleep  so  as  to  suit 
our  particular  circumstances.  The  important  point  is, 
that  once  the  habit  is  established,  say  of  going  to  sleep  at 
11  p.m.,  it  asserts  itself  with  some  insistence  unless  the 
attention  is  strongly  diverted.  In  the  course  of  a  short 
time,  varying  with  the  individual,  the  rhythm  can  be 
changed  and  the  man  sleeps  as  soundly  (other  things  equal) 
by  day  as  he  formerly  did  by  night. 


THE  WONDER   OF  LIFE  495 

Animals  accustomed  to  sleep  will  die  in  a  few  days  if 
they  are  deprived  of  it ;  in  some  cases,  much  .sooner,  as 
has  been  shown  experimentally,  than  if  they  are  deprived 
of  food.  What,  then,  is  it  that  goes  on  during  sleep  that 
makes  it  necessary  ?  What  is  the  physiological  condition 
during  sleep  ? 

In  a  recent  lecture,  Legendre  summed  up  the  state  of 
affairs  : — Digestion  goes  on,  and  this  may  lessen  the  blood- 
supply  to  the  brain ;  perspiration  and  excretion  go  on ; 
the  respiratory  movements  are  altered,  being  usually 
slower,  deeper,  and  more  regular ;  relatively  less  carbonic 
acid  is  given  off  ;  the  body  temperature  falls ;  the  action 
of  the  heart  is  slowed  and  the  arterial  blood  pressure 
diminishes ;  there  is  a  relative  angemia  of  the  brain ;  the 
working  of  the  sense-organs  is  altered ;  the  muscles  are 
generally  relaxed  and  the  reflexes  tend  to  disappear ; 
and  there  are  other  differences  of  a  subtler  sort.  But  it 
cannot  be  said  that  there  is  in  this  narration  anything 
that  in  particular  gives  us  the  clue  to  the  significance  of 
sleep. 

There  is  a  superabundance  of  theories  in  regard  to  the 
cause  of  sleep,  but,  until  recently,  it  was  the  delight  of 
physiologists  to  show  that  none  of  them  was  adequate. 
It  has  been  suggested  that  a  relative  anaemia  of  the  brain 
left  the  nerve-cells  without  enough  of  food  or  encumbered 
with  imperfectly  removed  waste.  It  has  been  suggested 
that  changes  in  the  condition  of  the  blood  produced  sleep. 
It  has  been  suggested  that  wearied  nerve-cells  contracted 
and  lost  that  touch  with  one  another  that  they  have  during 
waking  hours.  It  has  been  suggested  that  the  creature 
becomes  irresponsive  and  indifferent  to  the  outside  stimuli 
that  keep  it  agog  in  its  waking  hours.  But,  as  Claparede 


496  THE  WONDER  OF  LIFE 

points  out,  these  suggestions  cannot  be  solutions ;  they 
simply  shunt  the  problem.  For  why  this  periodic  change 
in  the  now  of  blood  to  the  brain,  why  the  retraction  of  the 
nerve  cells,  why  the  unresponsiveness  to  outside  stimu- 
lation ? 

In  a  luminous  lecture  on  sleep,  Professor  Fraser  Harris 
distinguishes  four  types — chemical,  vascular,  sensory,  and 
psychic.  (1)  Sleep  may  be  due  to  fatigue- toxins,  the 
poisonous  waste-products  of  exertion,  just  as  it  may  be 
induced  by  drugs.  The  nerve- cells  in  the  brain  no  longer 
exhibit  their  normal  interlinking  (or  synapsis)  ;  there  is 
resistance  to  incoming  sensory  messages.  Men  fall  asleep 
in  the  saddle  or  on  forced  marches,  and  Holbein  fell  asleep 
when  swimming  the  Channel.  (2)  Sleep  may  be  due  to 
diminution  of  the  velocity  of  the  cerebral  blood  flow,  just 
as  may  occur  abnormally  in  some  kinds  of  fainting.  It  has 
been  shown  that  the  sleeping  brain  is  paler,  there  is  less 
blood  and  a  lower  blood  pressure.  Mosso  devised  an  ex- 
periment of  balancing  a  wide-awake  man  accurately  on  a 
table,  and  showed  that  when  he  fell  asleep  the  foot  end 
of  the  table  sunk — the  dip  indicating  the  depth  of  sleep. 
When  the  heart  is  excited  we  cannot  sleep.  (3)  Sleep 
may  be  due  to  sensory  changes,  to  an  increase  of  the 
'  resistance '  at  the  interlinking  (or  synapsis)  of  the  cells 
in  the  sensory  centres  of  the  fore-brain,  or  a  diminution 
of  conductivity  at  these  interlinkings.  When  sensations 
force  their  way  in  we  cannot  sleep.  (4)  Sleep  may  be  due 
to  the  absence  of  emotions  and  ideas ;  thus  stupid  people 
fall  asleep  easily.  As  Bergson  has  said,  we  do  not  go  to 
sleep  if  we  are  more  interested  in  anything  else  than  going 
to  sleep.  When  we  are  worried  we  cannot  sleep. 

Another  approach  to  the  problem  of  sleep  is  in  the  light 


THE  WONDER  OF  LIFE  497 

of  general  biological  facts.  All  activity  implies  a  using 
up  of  material,  a  using  up  of  oxygen,  and  the  formation 
of  waste-products.  The  nerve  cells  are  in  no  way  exempted, 
and  it  has  been  demonstrated  visually  that  the  brain- cells 
of  a  bee  that  has  been  working  hard  all  day  are  in  a  different 
condition  from  those  in  a  brain  that  has  been  resting. 
In  a  case  of  prolonged  insomnia  there  was  said  to  be  a 
disappearance  of  a  readily  stainable  (chromatophilous) 
substance  located  in  what  are  called  '  Nissl's  granules ' 
in  most  nerve-cells.  Moreover,  the  nerve-cells  require  to 
keep  up  a  store  of  intra- molecular  oxygen.  And  besides 
carbonic- acid  gas,  which  is  always  being  removed  by  the 
blood,  there  are  subtler  wastes,  '  fatigue  toxins ',  about 
which  we  do  not  know  very  much.  The  general  biological 
view  is  therefore  this,  that  persistent  activity  involves 
using  up  of  material  and  oxygen  and  an  accumulation  of 
waste-products,  such  that  the  '  machinery  '  has  to  go  more 
slowly,  so  that  re- stoking  and  cleaning  may  be  thoroughly 
effected.  It  is  conceivable,  indeed,  that  it  might  have  been 
arranged  that  repair  always  kept  pace  with  waste,  and  that 
the  organism  never  got  into  any  physiological  arrears  at 
all.  It  is  probable  that  very  simple  organisms,  such  as  the 
'  immortal '  Amoeba  are  in  this  happy  state.  But  with 
increasing  complexity  this  ceased  to  be  possible,  and  sleep 
was  invented.  '  Blessed  be  the  man  ',  said  Sancho  Panza, 
'  who  invented  sleep  ',  but  we  do  not  know  at  what  precise 
level  of  organization  the  invention  was  discovered.  Prob- 
ably not  until  the  cerebral  cortex  was  well  differentiated. 

The  general  biological  theory  is  consistent  with  many 
familiar  facts  : — The  greatly  fatigued  organism  falls  asleep  ; 
it  awakens  from  sleep  refreshed.  And  it  is  remarkably 
confirmed  by  Legendre's  delicate  experiment  of  injecting 

K  K 


498  THE  WONDER  OF  LIFE 

into  a  normal  animal  the  serum,  or,  better,  the  cerebro- 
spinal  fluid  of  an  animal  exhausted  by  loss  of  sleep.  In 
about  half  an  hour  there  is  induced  an  imperative  need  for 


'  The  animal  so  injected  is  benumbed  little  by  little,  its 
eyelids  blink,  its  limbs  relax,  its  eyes  close,  it  loses  all 
attention,  and  it  responds  but  feebly  to  strong  stimulation. 
Its  brain  presents  the  characteristic  lesions  of  insomnia. 
The  injections,  under  the  same  conditions,  of  liquids  from 
a  normal  animal  have  no  effect  at  all '. 

It  seems  evident,  then,  that  in  some  form  or  other,  the 
injection  from  the  exhausted  animals  acts  like  a  sleeping 
draught. 

It  seems  to  us  very  probable  that  there  are  many  cases 
where  this  general  biological  theory  of  sleep  is  quite  suffi- 
cient. The  successful  long-lived  animals  are  those  that 
can  take  rests.  There  has  been  an  age-long  selection  of 
the  methodical,  who  work  when  they  work,  and  rest  when 
they  rest.  An  established  rhythm  of  alternate  working 
and  resting  pays  best,  and  it  has  become  conveniently 
hitched  on  to  the  great  external  periodicity  of  day  and 
night.  The  works  have  to  be  slowed  down  to  permit  of 
re-stoking  and  thorough  cleaning,  and  these  functions  are 
effected  most  readily  when  their  recurrence  is  rhythmic. 

It  is  very  interesting,  however,  to  find  Legendre,  physiolo- 
gist as  he  is,  declaring  that  although  physiology  has  im- 
portant and  fundamental  contributions  to  offer  towards 
a  theory  of  sleep, '  physiology  alone  cannot  dream  of  solving 
the  problem  '.  We  understand  that  his  view  has  particular 
reference  to  Man  and  the  higher  vertebrates,  where  it  seems 
that  psychological  factors  must  also  be  taken  into  account. 


THE  WONDER  OF  LIFE  499 

It  appears  to  us  probable,  as  we  have  hinted,  that  there  are 
levels  in  the  animal  kingdom  at  which  the  purely  physio- 
logical theory  of  sleep  is  adequate  to  cover  all  the  facts.  All 
sleep  is  not  the  same  sleep,  any  more  than  all  flesh  is  the 
same  flesh. 

Claparede  objects  to  the  purely  physiological  view  on 
various  grounds.  One  can  sleep  without  being  fatigued, 
and  one  may  be  too  tired  to  sleep.  If  sleep  were  enforced 
by  the  accumulation  of  fatigue-poisons,  how  is  it  that 
many  a  man  is  so  lively  just  a  few  minutes  before  he  goes 
to  bed  ?  Could  an  auto-intoxication  of  the  severity  sug- 
gested be  endured  night  after  night  for  threescore  years  and 
ten  ?  One  of  the  Siamese  twins  could  sleep  while  the  other 
suffered  from  insomnia,  yet  their  blood-vessels  communi- 
cated !  Perhaps  there  are  answers  to  these  objections, 
but  we  shall  not  go  into  that.  Our  point  is  simply  to  show 
that  there  are  great  difficulties  in  the  way  of  the  purely 
physiological  theory.  Claparede  maintains  that  an  adequate 
theory  must  be  psychological  as  well. 

Experiments  made  by  Legendre  and  Pieron  confirm 
the  theory  that  specific  waste-products  or  fatigue-toxins 
are  formed  during  periods  of  prolonged  wakefulness,  that 
these  permeate  the  organism,  and  particularly  affect  the 
frontal  lobes  of  the  brain.  They  prevented  dogs  from 
sleeping,  while  tiring  them  as  little  as  possible,  and  found 
that  about  ten  days  was  the  limit  of  resistance. 

'  The  temperature  of  the  body  remains  normal,  the  res- 
piration undergoes  no  variation,  and  the  amount  of  carbon 
dioxide  in  the  blood  does  not  increase,  which  enables  us 
to  exclude  the  theories  of  the  impoverishment  of  the  blood 
in  oxygen  and  its  enrichment  in  carbon  dioxide  as  the  actual 
causes  of  sleep.  Neither  the  blood  nor  the  brain  lose  their 


500  THE  WONDER  OF   LIFE 

proportion  of  water,  and  this  fact  combats  the  theories 
that  explain  sleep  by  dehydration  '. 

When  the  animal  can  no  longer  keep  its  eyes  open,  and 
has  become  almost  quite  unresponsive,  the  frontal  lobe 
shows  cellular  disturbances.  If  it  is  no  longer  kept  awake, 
it  plunges  into  deep  sleep,  from  which  it  awakens  com- 
pletely refreshed.  It  is  quite  normal  again,  and  the  alter- 
ations in  the  brain  have  disappeared.  It  may  be  that 
these  experiments  are  on  the  way  to  the  discovery  of  an 
alleviation  of  one  of  the  most  terrible  of  human  ills — 
insomnia. 

Claparede's  view  is  that  sleep  is  more  than  a  passive 
obedience  to  internal  physiological  necessities,  it  is  an 
active  defensive  instinct.  Just  as  the  bird  migrates  in 
autumn  before  there  is  external  coercion,  so  we  go  to  sleep 
before  there  is  an  overpowering  need.  The  physiological 
conditions,  such  as  the  fatigue-producing  substances,  pull 
the  trigger  of  an  old-established  sleep-instinct.  They 
serve  to  make  us  take  for  the  time  being  a  great  interest 
in  sleep.  If  a  greater  interest  should  be  aroused,  sleepiness 
disappears  like  magic  ;  the  child  who  could  hardly  keep  its 
eyes  open,  does  not  want  to  go  to  bed  at  all  when  there  is 
sudden  news  of  a  great  fire  to  be  seen.  When  our  interest 
for  the  moment  is  greater  in  sleep  than  in  anything  else, 
and  that  implies  inducing  external  and  internal  conditions 
to  which  we  have  become  habituated,  then  we  are  asleep 
before  we  know  it. 

It  comes  to  this,  that  long  ago,  those  animals  got  on  best 
which  established  a  rhythm  of  work  and  rest,  corresponding 
on  the  whole  to  the  periodicity  of  day  and  night,  and  later 
on  that  some  of  their  successors  got  on  best  which  developed 


THE  WONDER  OF  LIFE  501 

a  sleep-instinct  or  hereditary  predisposition  to  sleep, 
obedient  rather  to  trigger-pulling  physiological  conditions 
than  to  coercive  auto-intoxication  or  the  like. 

We  cannot  conclude  this  section  on  sleep  without  sug- 
gesting the  desirability  of  trying  to  bring  numerous  dis- 
tantly or  nearly  related  phenomena  into  line.  A  great 
reward  awaits  the  successful  investigator.  Perhaps  it 
is  impossible  to  put  the  numerous  analogous  phenomena 
into  any  one  series,  but  it  would  be  progress  to  know  why 
this  could  not  be.  If  we  start  with  normal  diurnal  sleep, 
we  have  many  associated  phenomena,  such  as  (a)  very 
prolonged  slumbers,  (6)  trance,  (c)  coma,  (d)  hibernation, 
(e)  prolonged  latent  life.  If  we  go  back  again  to  normal 
diurnal  sleep,  we  have  in  another  direction,  or  perhaps  in 
other  directions,  such  phenomena  as  fainting,  catalepsy, 
the  so-called  sleep  of  insects,  '  feigning  death ',  paralysis. 
And  then  there  are  the  various  forms  of  artificial  ansesthesia, 
such  as  chloroforming  (which  has,  of  course,  been  very 
thoroughly  studied),  to  '  the  shortest  way  out  of  Slum- 
town  ',  (which  has  been  very  thoroughly  practised). 

THE  SUBTLETY  OF  LIFE 

One  of  the  most  striking  biological  discoveries  of  the 
twentieth  century  is  that  of  anaphylaxis — a  difficult  term 
for  a  very  remarkable  phenomenon  which  illustrates  ex- 
ceedingly well  what  we  venture  to  call  the  subtlety  of  life. 
To  understand  what  the  phenomenon  is,  some  introductory 
exposition  is  necessary. 

It  is  well  known  that  certain  common  infectious  diseases, 
such  as  scarlet  fever,  produce  a  poison  within  the  body, 
and  that  if  the  patient  recovers  he  is  for  the  future  (in  most 


502  THE  WONDER  OF  LIFE 

cases)  invulnerable  or  '  immune  '  so  far  as  that  particular 
poison  is  concerned.  In  conquering  the  poison  of  the 
disease  the  body  produces  anti-toxins,  which  remain  as  a 
chemical  body-guard,  preventing  the  same  disease  from 
getting  in  again.  In  a  similar  way  the  anti-toxin 
produced  as  a  reaction  to  the  mild  poison  introduced  in 
vaccination  is  a  preventive  or  an  immunization  against 
subsequent  poisoning  from  small-pox.  This  is  the  first 
point  to  be  apprehended. 

It  is  also  very  well  known  that  there  are  many  poisons, 
such  as  the  nicotine  of  tobacco,  which  render  the  individual 
increasingly  tolerant  of  them  if  their  use  is  persisted  in. 
Thus,  the  confirmed  '  opium-eater '  can  imbibe  or  inject 
a  dose  which  would  immediately  kill  a  normal  individual, 
and  which  would  have  been  fatal  to  himself  if  he  had  not 
accustomed  himself  to  gradually  increased  quantities.  De 
Quincey,  in  his  Confessions,  tells  us  that  he  gave  to  a 
wandering  Malay  who  came  to  his  door,  a  piece  of  opium 
large  enough  to  kill  six  dragoons  and  their  horses  if  they 
were  not  used  to  it !  The  Malay  received  it  with  delight, 
broke  it  into  three  pieces,  and  immediately  swallowed 
them  all.  De  Quincey's  own  allowance  at  one  period  of 
his  life  was  said  to  be  eight  thousand  drops  of  laudanum  a 
day.  In  any  case,  it  is  certain  that  the  body  becomes 
increasingly  tolerant  of  certain  poisons. 

Anaphylaxis. — The  new  fact  which  has  been  discovered 
by  the  eminent  French  physiologist,  Professor  Charles 
Bichet,  is  that  certain  poisons  when  introduced  into  the 
system  enormously  increase  the  susceptibility  of  the  organ- 
ism to  the  toxic  action  of  that  particular  substance.  This  fact 
was  apparently  not  unknown  to  some  of  the  earlier 
physiologists,  but  it  was  not  clearly  recognized  as  other 


THE   WONDER  OF  LIFE  503 

than  an  obscure  anomaly  (always  a  clue  to  be  followed 
up),  till  Kichet  tackled  it  in  1902,  and  coined  for  it  the 
name  Anaphylaxis — a  companion  word  to  prophylaxis, 
which  means  protection  against  a  disease.  (See  Richet's 
V AnapTiylaxie,  Paris,  1912.) 

Let  us  follow  Professor  Richet's  work.  One  of  his  early 
experiments  was  with  the  poison  in  the  stinging  cells 
of  the  sea-anemone's  tentacles — a  poison  which  we  can  feel 
if  we  have  the  courage  to  put  the  tip  of  our  tongue  to  the 
sea-anemone's  mouth.  Our  finger  will  not  suffice,  for  the 
poison- bathed  lassoes  of  the  stinging  cells  are  not  suffi- 
ciently strong  to  penetrate  the  skin  of  our  hands.  Richet 
made  an  extract  by  soaking  the  tentacles  of  Actinia  in 
glycerine,  and  he  injected  the  poison  thus  obtained 
into  the  veins  of  a  dog.  He  found  that  a  rather  large  dose 
was  required  to  cause  death,  but  what  came  to  him  as  a 
surprise  was  the  discovery  that  a  dog  which  had  fully 
recovered  from  treatment  and  was  subjected  to  a  fresh  injec- 
tion a  month  afterwards,  succumbed  to  a  dose  of  about  one- 
twentieth  the  original  strength.  It  might  be  suggested 
that  the  poison  was  cumulative,  and  that  the  second  dose 
was  the  last  straw  that  broke  the  camel's  back,  but  the 
improbability  of  this  was  evidenced  by  the  time  that  had 
elapsed  since  the  previous  injection  and  by  the  smallness 
of  the  second  dose.  The  only  possible  conclusion  from 
this  and  other  experiments  was,  that  the  first  dose  brings 
about  a  peculiar  physiological  condition  which  makes  the 
organism  hyper-sensitive  to  subsequent  doses. 

A  further  step,  was  taken  in  1903,  when  M.  Arthus 
showed  that  the  anaphylactic  condition  could  be  induced 
by  a  substance,  such  as  blood-serum,  which  is  not  in  itself 
toxic.  A  rabbit,  which  had  been  injected  with  a  dose  of 


5o4  THE  WONDER  OF  LIFE 

horse-serum  without  showing  any  signs  of  disturbance, 
a  month  later  succumbed  at  once  on  receiving  an  injection 
of  one-twentieth  the  quantity  of  the  original  amount. 

Anaphylaxis  is  invariably  specific.  That  is  to  say,  an 
animal  which  has  been  rendered  hyper-sensitive  to  one 
particular  substance,  is  not  affected  in  any  peculiar  way  by 
a  subsequent  injection  of  another  substance,  not  even  by 
a  different  kind  of  blood-serum.  This  has  a  curious  appli- 
cation in  the  practice  of  medical  jurisprudence.  It  supplies 
a  new  and  conclusive  method  of  determining  the  source  of 
a  quantity  of  blood,  for  instance  whether  it  is  human  or 
not.  Suppose  there  be  in  readiness  a  set  of  guinea-pigs 
which  have  been  treated,  a  month  or  so  before,  with  large 
doses  of  the  serum  of  different  creatures — man,  dog,  horse, 
and  so  on ;  a  solution  of  the  blood  to  be  identified  is 
injected  into  each  of  them  ;  one  reacts  and  the  others 
remain  unaffected ;  the  blood  to  be  identified  came  from 
the  kind  of  organism  whose  serum  had  been  injected 
into  the  guinea-pig  which  reacted. 

Another  remarkable  experiment  was  made  with  guinea- 
pigs — for  here,  as  in  other  cases,  this  stupid  rodent  justifies 
its  existence  by  proving  a  remarkably  fine  subject  for 
experiment.  Its  sensitiveness  to  a  given  substance  may 
be  increased  five  thousand  times,  which  makes  very  delicate 
testing  possible.  The  experiment  was  that  of  injecting 
into  a  set  of  guinea-pigs  an  extract  of  the  muscle  of  a  human 
mummy,  and  after  an  interval  other  muscle  extracts  from 
various  organisms.  But  the  guinea-pigs  proved  the 
specific  nature  of  anaphylaxis,  they  reacted  only  to  extract 
of  human  muscle,  '  thus  proving,  if  proof  were  needed,  that 
the  chemical  constitution  of  the  human  body  has  not 
notably  varied  in  the  last  three  or  four  thousand  years '. 


THE  WONDER  OF  LIFE  505 

The  medical  aspects  of  anaphylaxis  do  not  concern  us 
here,  but  we  may  note  that  Professor  Richet  regards  the 
phenomenon  as  throwing  light  on  the  diagnostic  value  of 
tuberculin,  and  probably  also  on  the  occasional  terrible 
accidents  which  for  a  time  almost  discredited  it  as  a  thera- 
peutic agent.  This  latter  point  is  still  under  investigation. 
The  '  serum  disease  ',  too,  which  sometimes  follows  the 
use  of  anti- toxin  and  inoculation  for  plague  is  probably 
to  be  explained  in  the  same  way.  Cases  are  described 
which  seem  to  show  that  a  substance  may  be  prophylactic 
against  a  particular  disease,  bringing  about  a  condition  of 
immunity,  and,  at  the  same  time,  anaphylactic  against 
itself,  inducing  hyper-sensitiveness  to  even  small  doses. 
The  simultaneous  development  of  immunity  and  anaphy- 
laxis may  serve  to  illustrate  what  we  mean  by  the 
subtlety  of  life.  From  a  practical  point  of  view  it  is 
comforting  to  learn  that  the  physiologists  have  already 
devised  an  '  anti-anaphy lactic  method  of  procedure  '. 

No  crystallizable  substance  is  known  to  produce  anaphy- 
laxis, but  almost  any  colloid  substance  (i.e.  an  albuminoid 
unable  or  hardly  able  to  pass  through  organic  membranes) 
may  do  so  under  certain  conditions.  Among  these  con- 
ditions are,  that  a  certain  time — an  incubation  period — 
must  elapse  between  the  doses,  and  that  the  substance 
— serum,  egg,  milk,  muscle-extract,  vegetable  extract, 
sea-anemone  extract,  or  whatever  it  may  be — must  be 
introduced  into  the  circulation.  '  Alimentary  anaphy- 
laxis ',  i.e.  through  eating  the  substance  in  question,  seems 
to  come  about  very  rarely,  and  the  reason  for  this  is  obvious, 
since  it  is  not  the  substance  itself,  but  the  result  of  the 
digestion  of  the  substance,  that  passes  from  the  food-canal 
into  the  circulation.  But  the  rare  exceptions  are  of  great 


506  THE  WONDER  OF  LIFE 

interest,  since  they  are  the  people  known  to  us  all,  to  whom 
'  eggs  are  poison ',  who  cannot  digest  milk  in  any  form, 
or  who  cannot  eat  a  particular  kind  of  shellfish  without 
more  or  less  serious  symptoms,  such  as  nettlerash  and 
fever.  Instances  are  known  of  people  becoming  very 
seriously  ill  through  having  unconsciously  partaken  of  some 
disguised  form  of  the  substance  to  which  they  have  such 
a  violent  constitutional  antipathy.  A  scientific  light  is 
thrown  on  the  adage,  '  what  is  one  man's  food  is  another 
man's  poison  '.  In  this  connection,  again,  the  phenomenon 
of  anaphylaxis  is  absolutely  specific,  and  Dr.  Bichet  cites 
the  case  of  a  man  who  always  showed  violent  symptoms 
after  eating  even  a  perfectly  fresh  shrimp,  yet  who  could 
indulge  freely  in  lobster  without  inconvenience.  He 
strained  at  a  gnat,  but  could  swallow  a  camel  with  ease. 

Another  complexity  is  what  is  called  '  passive  anaphy- 
laxis '.  That  is  to  say,  if  the  blood  of  an  animal  which 
has  been  anaphylactized  in  regard  to  a  particular  sub- 
stance be  injected  into  another  animal,  that  also  becomes 
anaphylactic  to  the  same  substance.  A  little  seems  to 
go  a  long  way  in  producing  a  remarkable  change.  Inter- 
esting also  is  the  fact  that  anaphylaxis  in  a  mother,  acquired 
either  before  or  after  conception,  may  be  acquired  by  her 
offspring,  so  that  they  are  born  anaphylactic.  Diffusion 
of  a  substance  from  the  mother's  blood  to  the  offspring's 
must  have  occurred  during  the  ante-natal  life.  But  the 
condition  of  congenital  anaphylaxis  is  not  of  long  duration. 
In  guinea-pigs  it  was  noted  on  the  forty-fourth  day,  but 
had  disappeared  by  the  seventieth. 

Professor  Kichet's  theory  of  anaphylaxis,  that  is  of  the 
precise  way  in  which  the  condition  is  brought  about,  is 
too  technical  for  our  present  purpose.  Suffice  it  to  say 


THE  WONDER  OF  LIFE  507 

that  he  regards  the  first  introduction  of  the  albuminoid 
substance  as  modifying  the  blood  by  producing  in  it, 
during  the  so-called  incubation  period,  a  chemical  sub- 
stance, which  is  not  in  itself  toxic,  but  which  is  capable  of 
becoming  immediately  and  violently  toxic  in  the  presence 
of  the  original  albuminoid. 

Chemical  Individuality. — One  of  the  general  ideas 
that  rises  in  the  mind  after  a  consideration  of  some  of  the 
facts  of  anaphylaxis,  is  that  of  the  chemical  individuality 
of  an  organism.  It  is  characteristic — fundamentally 
characteristic — of  an  organism  that  it  carries  its  past  into 
its  present,  that  '  time  bites  into  it '  as  Bergson  puts  it, 
and  there  is  often  very  considerable  variety  in  individual 
experience.  Many  different  kinds  of  substances  enter  into 
the  organism,  and  some  of  them  may  bring  about  modifica- 
tion, either  in  the  direction  of  anaphylactization  or  immuni- 
zation, and  thus  each  individual  of  a  species  may  differ 
from  every  other  in  chemical  composition.  We  know 
indeed  experimentally  that  there  are  these  individual 
differences,  some  of  them  probably  germinal  or  innate, 
some  of  them  modificational  or  extrinsic,  in  origin.  An 
individual  is  an  individual  not  only  to  his  finger-prints, 
but  to  his  chemical  molecules.  And  it  seems  to  us  that 
the  anaphylaxis  experiments  clearly  show  that  the  vague 
'  idiosyncrasy '  of  the  past  must  give  place  to  a  more 
definite  conception  of  a  chemical  individuality  which  not 
only  expresses  the  new  unity  which  is  established  in  every 
fertilized  egg-cell,  but  embodies  the  results  of  the  indivi- 
dual's physiological  history,  just  as  his  psychological 
personality  is  ever  registering  his  mental  experiences. 

But  while  there  are  minor  idiosyncrasies  (distinguishing 
between  the  individual  members  of  a  species,  distinguish- 


508  THE  WONDER  OF  LIFE 

ing  sometimes  between  the  two  sexes),  there  is  also  a 
typical  specific  chemical  constitution  which  cannot  be 
widely  departed  from  if  the  species  is  to  persist.  The 
muscle  extract  of  a  modern  man  pulled  the  anaphylactic 
trigger  in  the  guinea-pig  which  had  been  treated  a  month 
before  with  extract  of  mummified  muscle.  We  know  in 
other  connections  that  there  is  a  demonstrable  specific  differ- 
ence between  the  blood  of  a  horse  and  the  blood  of  an  ass. 
There  is  a  specific  chemical  constitution  which  is  on  the 
whole  the  best  for  the  species  in  question,  being  stamped 
with  survival-merit  after  thousands  of  disadvantageous 
aberrations  have  been  sifted  away  through  thousands  of 
years.  Thus  we  come  back  from  anaphylaxis  to  what  was 
said  of  old  :  '  All  flesh  is  not  the  same  flesh  :  but  there  is 
one  kind  of  flesh  of  men,  another  flesh  of  beasts,  another  of 
fishes,  and  another  of  birds '.  We  are  here  close  to  the 
idea  of  a  chemical  definition  of  a  species,  which  will  not 
be  other  than  complementary  to  a  psychological  one.  And 
it  is  here  that  Professor  Bichet  makes  a  notable  contribution, 
pointing  out  the  specific  or  racial  value  of  this  curious  pro- 
perty of  anaphylaxis. 

'  I  am  more  and  more  convinced  ',  he  writes,  '  that  every 
detail  of  the  organism  has  a  protective  role,  and  is  useful 
and  even  necessary  to  life,  and  that,  therefore,  a  great 
general  biological  function  like  anaphylaxis  must  play 
an  essential  part  in  the  defence  of  organisms.  So  that 
anaphylaxis  appears  to  us  an  efficacious  and  energetic 
method  of  maintaining  the  chemical  stability  of  our  bodies 
by  provoking  an  immediate  and  violent  reactional  response 
to  the  introduction  of  any  substance  which  might  change 
it.  This  is  not  the  defence  of  the  individual ;  it  is  the 
defence  of  the  species  at  the  cost  of  the  individual '. 


THE  WONDER  OF  LIFE  509 

Individuality  of  the  Blood. — What  is  called  the  serum 
test  for  blood  is  a  good  illustration  of  the  subtle  individu- 
ality of  different  creatures.  If  the  serum  of  human  blood 
is  injected  into  a  rabbit,  it  produces  a  change  in  the  rabbit's 
blood  of  a  very  specific  kind.  As  de  Nobele  showed  in 
1902,  the  serum  of  that  rabbit  will  give  a  precipitate  with 
human  blood,  but  not  with  the  blood  of  other  Mammals. 
Thus  if  a  murderer  asserts  that  the  bloodstains  on  his 
clothes  are  due  to  his  having  killed  a  rabbit,  not  a  man, 
his  statement  can  be  tested ;  and  the  method  has  passed 
into  the  ordinary  practice  of  medical  jurisprudence.  The 
serum  for  testing  with  can  be  kept  for  months  in  a  dry  state 
(after  evaporation  in  a  vacuum)  without  losing  its  relia- 
bility, and  bloodstains  that  are  several  months  old  may 
be  accurately  identified.  Of  course  the  method  has  been 
tested  and  re-tested  hundreds  of  times,  and  little  improve- 
ments in  detail  have  been  introduced.  It  should  be 
noticed  that  the  principle  of  the  method  was  discovered 
in  relation  to  milk,  and  that  it  was  applied  in  the  identifica- 
tion of  different  kinds  of  milk  and  different  kinds  of  flesh 
before  it  was  applied  to  blood. 

ADAPTATION 

Wherever  we  look  throughout  the  wide  world  of  animate 
nature,  we  find  illustrations  of  particular  fitness  to  parti- 
cular conditions.  The  size,  the  shape,  the  colour  of  an 
organism,  the  structure  of  parts  in  relation  to  their  use 
and  in  their  relation  to  other  parts — all  are  adaptive.  In 
the  same  way  the  characteristic  behaviour  of  the  creature 
in  its  everyday  life,  and  the  internal  activities  within  the 
body — all  are  adaptive.  And  what  is  true  of  everyday 


5io  THE  WONDER  OF  LIFE 

activities,  where  one  might  attribute  some  of  the  effective- 
ness to  practice,  is  equally  true  of  activities  which  are  only 
occasional,  e.g.  those  connected  with  animal  courtship 
and  parenthood.  Almost  every  detail  of  specific  structure 
and  specific  behaviour  may  be  interpreted  as  adaptive. 
This  term  might  simply  mean  that  the  structure  or  function 
in  question  is  fit,  effective,  well  adjusted,  making  for  the 
preservation  or  well-being  of  the  individual  or  of  the  species  ; 
but  in  biological  usage  it  has  also  a  theoretical  implication 
— that  the  detail  in  question,  if  it  be  part  of  the  hereditary 
constitution  or  some  expression  of  it,  is  the  result  of  a 
process  of  evolution.  It  was  not  always  as  it  is  now,  it  has 
a  history  behind  it,  it  is  a  product  of  the  factors  of  evolu- 
tion, whatever  these  may  be. 

There  can  be  no  doubt  that  no  small  part  of  the  pleasure 
we  have  in  the  contemplation  of  living  creatures  is  related 
to  their  effective  fitness.  As  Sir  J.  Burdon  Sanderson  once 
said  in  a  lecture,  '  the  delight  and  interest  with  which  the 
forms,  colours,  and  structure  of  animals  and  plants  fill  us  is 
derived  from  the  conscious  or  unconscious  perception  by 
our  minds  of  their  adaptation — their  fitness  for  the  place 
they  are  intended  to  occupy '.  He  even  went  so  far  as  to 
declare  his  belief  that  our  artistic  perception  of  beauty 
in  nature  is  in  great  measure  derived  from  the  same  source. 

In  working  towards  a  clear  idea  of  one  of  the  fundamental 
facts  of  biology — the  adaptiveness  of  structure  and  func- 
tion— it  may  be  useful  to  consider  three  other  facts — 

(1)  Effectiveness  of  response;  (2)  plasticity;  and 
(3)  modifiability. 

(1)  Effectiveness  of  response. — As  we  have  already 
seen,  effectiveness  of  response  is  one  of  the  distinctive  pecu- 
liarities of  living  creatures.  Many  inanimate  things 


THE  WONDER  OF  LIFE  511 

respond  to  stimuli,  but  often  self-destructively,  whereas 
the  living  creature's  responses  tend  to  self-preservation 
or  to  species-preservation.  Not  that  the  organism  can 
respond  successfully  to  all  stimuli,  for  instance  to  a  strong 
current  of  electricity,  for  it  is  not  able  to  live  anywhere  or 
anyhow,  but  only  within  certain  environmental  limits. 
We  cannot  account  for  this  primary  and  fundamental 
power  of  effective  response ;  it  is  part  of  our  conception 
of  life.  There  could  have  been  no  organisms  at  all  unless 
they  had  possessed  something  of  this  power  of  answering 
back  and  yet  retaining  their  integrity.  In  some  degree  it 
must  have  been  part  and  parcel  of  the  first  and 
simplest  organisms,  and  it  has  been  improved  upon  ever 
since. 

(2)  Plasticity. — Another  important  fact  is  that  living 
creatures  are  in  different  degrees  plastic.  That  is  to  say, 
they  can  adjust  their  reactions  to  novel  conditions,  they 
are  not  rigidly  stereotyped  in  their  responses.  In  many 
cases,  even  among  the  simplest  organisms,  the  animal  that 
is  up  against  a  difficulty,  '  tries  '  one  mode  of  reaction 
after  another,  and  may  eventually  find  one  which  is  effective. 
Professor  Jennings  reports  that  the  behaviour  of  certain 
Infusorians  may  be  compared  to  a  pursuance  of  '  the 
method  of  trial  and  error '.  There  are  not  a  few  cases  of 
marine  animals  showing  sufficient  plasticity  to  adjust 
themselves  in  their  own  individual  lifetime  to  the  very 
different  conditions  of  fresh  water.  We  see  plasticity 
too  when  animals  are  transported  from  one  habitat  to 
another  where  different  habits  are  required.  It  is  convenient 
to  use  the  term  '  accommodation  '  for  the  frequently  occur- 
ring functional  adjustments  which  organisms  are  able  to 
make  to  new  conditions.  Thus  there  may  be  an  interest- 


512  THE  WONDER  OF  LIFE 

ing  multiplication  of  red  blood  corpuscles  in  the  case  of 
successful  human  migrants  to  a  lofty  plateau, — in  South 
Africa,  for  instance. 

Many  unicellular  animals  are  very  plastic,  and  it  seems 
reasonable  to  suppose  that  there  was  a  considerable  prim- 
ary plasticity  in  the  early  organisms,  and  that  restrictions 
were  placed  on  this  as  differentiation  progressed.  As  the 
body  became  more  and  more  complex  the  range  of  primary 
plasticity  was  lessened,  but  a  more  specialized  secondary 
plasticity  was  gained  in  many  cases  where  organisms  lived 
in  environments  liable  to  frequent  vicissitudes. 

(3)  Modifiability. — Taking  a  third  step  we  recognize 
as  a  fact  of  life  that  organisms  often  exhibit  great  modifia- 
bility.  They  can  change  for  their  lifetime  in  response  to 
changes  in  surroundings  or  habits.  Thus  a  man's  skin 
may  be  so  thoroughly  tanned  by  exposure  to  the  sun  during 
half  a  lifetime  in  the  tropics,  that  it  never  becomes  pale 
again,  even  after  migration  to  a  far  from  sunny  clime.  This 
change  in  the  skin  is  a  modification  :  it  differs  from  a 
temporary  adjustment  in  being  permanent,  and  from  a 
constitutional  swarthiness  inasmuch  as  it  was  impressed 
from  without  rather  than  expressed  from  within.  It  is 
exogenous,  not  endogenous. 

'  Modifications '  may  be  defined  as  changes  in  the  body 
acquired  during  an  individual  lifetime  as  the  direct  result 
of  changes  in  function  or  in  environment,  and  so  transcend- 
ing the  limit  of  organic  elasticity  that  they  persist  after 
the  inducing  conditions  have  ceased  to  operate.  Lack  of 
nutrition  at  a  particular  stage  in  development  may  directly 
induce  an  arrest  or  a  dwarfing,  with  consequences  from 
which  there  is  no  possibility  of  recovery.  A  particular 
occupation,  such  as  shoemaking  or  the  old-fashioned  weav- 


THE  WONDER  OF  LIFE 


513 


ing,  may  induce  functional  changes  even  in  the  skeleton, 
which  are  there  for  life. 

These  modifications  are  sometimes  indifferent,  so  far  as 
we  can  judge,  as  regards  the  welfare  of  the  organism  ;  and 
though  they  are  almost  always  attempts  at  effectiveness 
on  the  part  of  the  structure  affected,  they  may  be  pre- 
judicial to  the  organism  as  a  whole.  In  the  case  of  a  goldfish 


FIG.  80. — Underside  of  a  young  flounder,  showing  pigmentation  after 
exposure  to  light  from  beneath.     (After  J.  T.  Cunningham.) 


shut  up  for  years  in  total  darkness,  there  is  degeneration 
of  the  eye,  which  is  no  doubt  a  modification  on  the  minus 
side.  Yet  the  degeneration  considered  by  itself  may  be 
regarded  as  a  quite  effective  response  to  the  abnormal 
conditions  involved.  The  inflammation  that  follows  an 
invasion  of  microbes  into  the  body  may  lead  on  to  death, 
but  it  is  none  the  less  an  effective  response  on  the  part  of 

L  L 


514  THE  WONDER  OF  LIFE 

the  body-guard  of  phagocytes,  and  it  is  often  a  life-saving 
one. 

In  many  cases  the  modifications  are  markedly  beneficial. 
When  a  mammal  is  taken  to  a  colder  climate  it  often 
acquires  a  thicker  coat  of  hair,  which  is  obviously  advan- 
tageous. When  a  plant  is  moved  from  the  plain  to  the 
plateau  it  often  acquires  a  thicker  epidermis,  and  Professor 
MacDougal  has  furnished  numerous  illustrations  of  useful 
modifications  exhibited  by  plants  when  transferred  to 
desert  conditions.  Every  one  knows  that  an  area  of  skin 
much  pressed  upon  becomes  hard  and  callous,  and  that  this 
is  often  of  protective  value.  Many  other  instances  might 
be  given  of  functionally  and  environmentally  induced 
modifications  which  are  useful,  effective,  fit,  and  may  even 
make  for  the  preservation  of  the  individual,  when  the 
struggle  for  existence  is  keen.  These  are  adaptive  modifica- 
tions. 

Nature  of  Adaptations. — It  tends  to  clearness  of  think- 
ing to  keep  the  term  adaptations  (used  to  denote  the  results 
of  an  evolutionary  process)  for  features  and  qualities  and 
arrangements  which  are  inborn,  not  individually  acquired. 
An  accommodation  is  the  transient  expression  of  plasticity  ; 
a  modification  is  permanent  but  individually  acquired ; 
an  adaptation  is  racial,  the  expression  of  the  natural  inherit- 
ance, not  an  individual  gain  or  loss.  It  goes  without  saying 
that  though  these  adaptations  are  potentially  implicit  in  the 
germinal  material — in  the  fertilized  ovum — they  cannot  be 
expressed  without  the  appropriate  nurture.  But  this  does 
not  bring  them  in  the  least  within  the  category  of  '  acquired 
characters '  or  modifications,  which  result  from  changes 
in  the  ordinary  nurture.  In  the  same  way,  it  is  mere 
word-splitting  to  find  any  difficulty  in  the  fact  that  ac- 


THE  WONDER  OF  LIFE  515 

quired  adaptive  modifications,  which  are  the  direct  results 
of  changes  in  the  ordinary  nurture,  could  not  occur  unless 
the  potentiality  of  them  were  part  of  the  heritable  '  nature  '. 
That  goes  without  saying,  but  it  does  not  affect  the  clear 
distinction  between  the  exogenously  induced  modification, 
wrought  from  without  inwards,  and  the  endogenously 
originating  variation  which  works  from  within  outwards. 

Origin  of  Adaptations. — Like  the  correlated  but  larger 
problem  of  the  origin  of  species,  this  is  one  of  the  funda- 
mental— still  imperfectly  answered — questions  which  the 
interpreter  of  animate  nature  has  to  face.  There  are  only 
two  main  theories  in  the  field — the  theory  of  the  direct, 
and  the  theory  of  the  indirect  origin  of  adaptations. 

(a)  According  to  the  Lamarckian  theory  racial  adapta- 
tions owe  their  origin  to  the  cumulative  inheritance  of 
individual  adaptive  modifications.  But  there  is  as  yet  a 
lack  of  positive  evidence  in  support  of  this  interpretation, 
plausible  as  it  seems  to  be.  Unless  we  have  experimental 
evidence  of  the  transmissibility  of  presently  occurring 
adaptive  modifications,  we  are  not  justified  in  using  this  as 
an  interpretation  of  results  which  occurred  in  the  distant 
past.  Too  much  may  be  made  of  the  argument  that 
many  cases  are  known  where  transmission  of  modifica- 
tions certainly  does  not  occur,  but  it  must  be  admitted 
that  it  is  difficult  in  our  present  state  of  knowledge  to 
conceive  of  any  way  by  which  a  change  acquired  by  a 
part  of  the  body  can  affect  the  germinal  material  in  a 
manner  so  precise  and  representative  that  the  offspring 
show  a  corresponding  change  in  the  same  direction. 

(6)  The  Darwinian  theory  is  that  adaptations  are  due 
to  the  selection  of  those  inborn  and  heritable  variations 
which,  by  making  their  possessors  better  adapted  to  the 


5ib  THE  WONDER  OF  LIFE 

conditions  of  their  life,  have  some  survival  value.  It  is  a 
fact  of  observation  that  in  many  groups  of  organisms  the 
individuals  fluctuate  continually  in  various  directions.  It  is 
also  a  fact  of  observation  that  some  of  these  variations 
increase  the  survival  value  of  their  possessors.  It  is 
inferred  that  the  cumulative  inheritance  of  these  favour- 
able variations,  fostered  by  selection  in  any  of  its  numerous 
forms,  and  helped  by  the  elimination — gradual  or  sudden 
— of  forms  lacking  the  variations  in  the  fit  direction,  or 
having  others  relatively  unfit,  may  lead  to  the  establish- 
ment of  new  adaptations.  The  greatest  difficulty  in  this 
argument  is  to  account  for  the  origin  of  the  fit  variations, 
and  this  has  to  be  met  by  the  accumulation  of  observational 
and  experimental  data  bearing  on  the  origin  and  nature 
of  variations.  It  is  also  necessary  to  accumulate  more 
facts  showing  that  selective  processes — acting  directively 
on  fluctuating  variations — do  really  bring  about  the  results 
ascribed  to  them. 

(c)  The  work  of  recent  years — notably  that  of  Bateson 
and  De  Vries — has  made  it  plain  that  besides  the  con- 
tinually occurring  '  fluctuating  variations,'  there  are  '  dis- 
continuous variations '  or  '  mutations,'  where  a  new  char- 
acter or  group  of  characters  not  only  appears  suddenly, 
but  may  come  to  stay  from  generation  to  generation.  It 
cannot  be  said  that  we  understand  the  origin  of  these 
mutations,  in  some  of  which  the  organism  in  many  of  its 
parts  seems  suddenly  to  pass  from  one  position  of  organic 
equilibrium  to  another  ;  but  that  they  do  occur  is  indubit- 
able, and  their  marked  heritability  is  also  certain.  Mendel 
has  given  at  once  a  demonstration  and  a  rationale  of  the 
fact  that  certain  mutations,  when  once  they  have  arisen, 
are  not  likely  to  be  swamped,  but  are  likely  to  persist, 


THE  WONDER  OF  LIFE  517 

unless,  of  course,  selection  is  against  them.  In  horticulture, 
in  particular,  artificial  selection  has  operated  in  great  part 
on  mutations.  If  this  interpretation  be  confirmed  and 
extended,  it  will  not  be  necessary  to  lay  such  a  heavy  burden 
on  the  shoulders  of  selection.  But  more  facts  are  urgently 
needed ;  and  how  and  under  what  conditions  mutations — 
whether  adaptive  or  non-adaptive — occur,  remains  an 
unsolved  problem. 

(d)  In  his  theory  of  Germinal  Selection,  Weismann  has 
elaborated  an  attractive  subsidiary  hypothesis.     Supposing 
that  the  germinal  material  consists  of  a  complex — a  multi- 
plicate — of  organ- determining  particles  (the  determinants), 
he  postulates  a  struggle  going  on  within  the  arcana  of  the 
germ-plasm.     Supposing   limitations   of   nutrition   within 
the  germ,  he  pictures  an  intra-germinal  struggle  in  which 
the  weaker  determinants  corresponding  to  any  given  part 
will  get  less  food  and  will  become  weaker,  while  the  stronger 
determinants  corresponding  to  the  same    part   will    feed 
better  and  become  stronger.     While  the  external  selection 
of  individuals  goes  on,  and  is  all  important,  it  is  being 
continually  backed  up  by  the  germinal  selection.     Thus 
nothing  succeeds  like  success. 

(e)  Various  evolutionists — Profs.  Mark  Baldwin,  H.  F. 
Osborn,  and  C.  Lloyd  Morgan — have  suggested  that  al- 
though  individual   adaptive   modifications   may   not   be 
transmissible,    they    may    have    indirect    importance    in 
evolution,  by  serving  as  life-preserving  screens  until  coin- 
cident inborn  or  germinal  variations  in  the  same  direction 
have  time  to  develop.     As  Groos  expresses  it,  in  reference 
to  some  instinctive  activities — Imitation  may    keep    a 
species  afloat  until  Natural  Selection  can  substitute  the 
life-boat  heredity  for  the  life-belt  of  tradition. 


518  THE  WONDER  OF  LIFE 

Finally,  in  thinking  over  this  difficult  problem  of  adapta- 
tions, we  must  remember  the  importance  of  the  active 
organism  itself.  As  Professor  James  Ward  has  well  pointed 
out,  it  may  seek  out  and  even  in  part  make  its  environment ; 
it  is  not  only  selected,  it  selects  ;  it  acts  as  well  as  reacts. 
And  although  the  details  and  finesse  of  this  may  have  been 
elaborated  in  the  course  of  selection,  the  primary  poten- 
tiality of  it  is  an  essential  part  of  the  secret  of  that  kind 
of  activity  which  we  call  Life. 

Illustrations  of  Adaptations. — The  structure  of  a  long 
bone  in  a  mammal  is  adapted  to  give  the  utmost  firmness 
with  the  minimum  expenditure  of  material ;  the  unique 
pollen-basket  on  the  hind  legs  of  worker-bees  is  adapted 
to  stow  away  the  pollen ;  the  colours  and  patterns  on  the 
wings  of  leaf-insects  are  adapted  to  harmonize  with  the 
foliage  on  which  they  settle  ;  the  parts  of  flowers  are  often 
adapted  to  ensure  that  the  insect- visitors  are  dusted  with 
pollen,  and  thus  to  secure  cross-fertilization ;  the  peacock 
is  adapted  to  captivate  the  pea-hen  ;  the  mother  mammal 
is  adapted  for  the  prolonged  pre-natal  life  of  the  young  ; 
the  so-called  '  egg-tooth  '  at  the  end  of  a  young  bird's  bill 
is  adapted  to  the  single  operation  of  breaking  the  egg-shell 
— and  so  on  throughout  the  whole  of  the  animate  world.  It 
is  indeed  a  mistake  to  dwell  upon  signal  instances  of  adapta- 
tions, since  (apart  from  degenerative  changes  in  old  age, 
morbid  processes,  perverted  instincts,  rudimentary  or 
vestigial  structures,  and  certain  'indifferent'  characters 
which  are  not  known  to  have  any  vital  significance)  almost 
every  detail  of  structure  and  function  may  be  regarded  as 
adaptive. 

The  Mole. — In  illustration  of  adaptive  characters  let 
us  consider  a  common  animal  like  the  mole,  '  the  little 


Pr 


FIG.  81.— Leaf-insects  (Phyllium)  From  a  specimen.  A,  the  green 
form  on  green  leaves  ;  B,  the  brown  form  on  brown  leaves  ; 
anH  C,  the  young  stage. 


5i8  THE  WONDER  OF  LIFE 

Finally,  in  thinking  over  this  difficult  problem  of  adapta- 
tions, we  must  remember  the  importance  of  the  active 
organism  itself.  As  Professor  James  Ward  has  well  pointed 
out,  it  may  swk  ont  and  even  in  part  make  its  environment  ; 
it  is  not  onlv  sekw-t*d,  it  selects  ;  it  acts  as  well  as  reacts. 
And  although  tk«*  details  and  finesse  of  this  may  have  been 
elaborated  ID  ibfc  course  of  selection,  the  primary  poten- 
tial itv  of  ;?  i«  «*ri  essential  part  of  the  secret  of  that  kind 
of  aeuviiv  \vfma  we  call  Life. 

IUustr*tta»*  of  Adaptations.  —  The  structure  of  a  long 

I,*,?,    .i..  >  !S;<Mtif«al  is  adapted  to  give  the  utmost  firmness 

•  *r<!uin  expenditure  of  material;    the  unique 

<*.  aft  the  hind  legs  of  worker-bees  is  adapted 

*'  *~ft*  the  pollen  ;   the  colours  and  patterns  on  the 

.ramiMqi  a  imrfl 
nv/oid  no  rrno^  nwoid  sril  ,fl 


peacock 

1  1  ed  to  ca  i  •  n  imal 

is  adapted  for  the  prolonged  pre-natal  life  of  the  young  ; 
the  so-called  '  egg-tooth  '  at  the  end  of  a  young  bird's  bill 
is  adapted  to  the  single  operation  of  breaking  the  egg-shell 
—  and  so  on  throughout  the  whole  of  the  animate  world.  It 
is  indeed  a  mistake  to  dwell  upon  signal  instances  of  adapta,- 
tions,  since  (apart  from  degenerative  changes  in  old  age. 
morbid  processes,  perverted  instincts,  rudimentary  or 
vestigial  structures,  and  certain  'indifferent'  chara-- 
which  are  not  known  to  have  any  vital  significance)  almost 
every  detail  of  struct-  '^tion  may  be  n 

adapt  - 

The  Mole.  —  In  illustration  of  ada 
u  -.  <••'  ..fi  animal  . 


THE  WONDER  OF  LIFE  519 

gentleman  in  the  velvet  coat ',  who  long  ago  discovered 
the  possibility  of  a  subterranean  life  for  a  warm-blooded 
animal,  and  disturbed  the  earthworms  in  the  retreats 
where  they  had  for  so  long  enjoyed  relative  immunity. 
What  a  bundle  of  adaptations  the  creature  is  !  The  out- 
turned  hand  has  become  a  powerful  shovel,  aided  by  the 
presence  of  an  extra  bone,  the  sickle,  to  the  inner  side'bf  the 
thumb  ;  the  shoulder-girdle  is  very  strong  and  the  pectoral 
muscles  are  those  of  an  athlete  ;  the  long  muscular  sensitive 
snout,  which  probes  the  way,  is  strengthened  by  a  special 
bone  near  the  tip  ;  the  hind  legs  remain  purely  locomotor  ; 
the  absence  of  the  external  trumpet  of  the  ear  is  an  adapta- 
tion to  the  reduction  of  friction  ;  the  minute  eyes  are  well 
hidden  among  the  hair  and  thus  saved  from  being  rubbed  ; 
and  there  must  be  some  special  advantage  too  in  the  way 
the  hairs  stand  out  vertically  like  the  pile  on  velvet.  The 
eye  is  not  well  finished,  as  an  instrument-maker  might 
say — the  lens  in  particular  being  rather  half-made  and  the 
optic  nerve  far  from  well  developed — but  as  the  mole  is 
well  aware  of  the  difference  between  light  and  darkness, 
and  can  bite  quite  deftly  at  a  dangled  worm,  its  eyesight 
is  probably  just  as  good  as  it  needs  to  be. 

Its  habits,  too,  how  adaptive  they  are — the  quick  hunt- 
ing close  to  the  surface,  the  slow  deep  burrowing  below  the 
reach  of  the  frost's  fingers  in  winter,  the  nest-making  below 
the  chief  mole-hill  or  fortress,  the  making  of  a  special 
tunnel  to  the  nearest  water,  and  so  on.  Dr.  Bitzema-Bos 
has  verified  the  observation  that  moles  make  a  store  of 
earthworms  for  the  winter  months,  biting  their  heads 
off  so  that  they  lie  inert  but  not  dead.  If  this  were  done 
in  the  summer  months  the  head  would  be  regrown 
and  the  captives  would  crawl  away,  but  below  a  certain 


520  THE  WONDER  OF  LIFE 

temperature  the  regrowth  does  not  occur,  and  the  decapi- 
tated earthworms  he  imprisoned  without  walls. 

Fly  Trap. — As  a  fine  example  let  us  take  Venus's 
Fly  Trap  (Dioncea  muscipula),  a  member  of  the  Sundew 
family  (Droseraceae)  in  which  we  find  a  graded  series  of 
adaptations  to  catching  and  digesting  insects.  The  trap 
of  Dionsea  is  the  much  modified  leaf.  The  blade  consists 
of  two  nearly  semicircular  halves,  united  by  a  strong  midrib ; 
the  surface  is  studded  with  reddish  glands,  and  bears  on 
each  side  three  sensitive  jointed  hairs  ;  on  each  margin 
there  are  about  twenty  spikes  directed  upwards  and 
inwards  ;  the  stalk  of  the  leaf  is  like  the  handle  of  a  tea- 
spoon with  a  channelled  upper  surface  and  a  narrow 
isthmus  where  it  joins  the  blade. 

When  an  insect,  attracted  to  the  glistening  glandular 
surface,  touches  one  of  the  upstanding  jointed  hairs,  the 
halves  of  the  blade  begin  at  once  to  close  in  upon  one 
another,  the  spikes  on  one  side  fitting  in  between  those 
on  the  other,  like  the  teeth  of  a  rat  trap.  This  happens 
quickly,  but  the  movement  stops  before  the  leaf  is  com- 
pletely closed — a  fact  which  Darwin  explained  ingeniously. 
Insects  of  small  size,  hardly  worth  catching,  escape  between 
the  crossed  teeth,  and  the  leaf  soon  re-opens.  A  larger 
victim,  unable  to  get  through  the  prison  bars,  touches  the 
sensitive  hairs  again  and  induces  a  second  and  more  vigor- 
ous contraction,  which  proves  fatal.  No  more  effective 
adaptation  could  be  imagined. 

Let  us  follow  the  story  a  step  further.  When  the  Venus 
Fly  Trap  is  tricked  into  closing,  it  opens  again  in  twenty- 
four  hours.  But  when  it  shuts  on  a  big  fly  it  remains  with 
the  two  lobes  pressed  against  one  another  for  a  week  or 
more.  The  secreting  glands  are  stimulated  and  pour  out 


THE  WONDER  OF  LIFE  521 

digestive  secretion ;  more  and  more  glands  join  in ;  and 
the  two  blades  bulge  outwards  partly  with  the  fly  and 
partly  with  the  copious  digestive  juice.  It  is  interesting 
to  notice  in  passing,  as  an  instance  of  the  unity  of  physio- 
logical processes  that  the  closing  of  the  Fly  Trap  leaf  is 
accompanied  by  an  electrical  change  similar  to  that 
associated  with  every  muscular  contraction. 

Snow  Shoes. — One  might  spend  a  pleasant  lifetime  in 
admiring  organic  adaptations,  and  even  the  most  matter- 
of-fact  man  must  admit  that  many  of  them  are  fine  examples 
of  attaining  effective  results  by  very  simple  means.  Take, 
for  instance,  the  '  snow  shoes  '  of  the  North  American 
Ruffed  Grouse  (Bonasa  umbellata).  According  to  Dr. 
Austin  Hobart  Clark,  these  '  snow  shoes '  develop  in 
winter  as  two  rows  of  skin  '  scutes  '  on  each  side  of  each 
toe,  and  they  increase  the  area  of  the  foot  by  as  much 
again.  They  remind  one  a  little  of  the  scolloped  margins 
of  the  toes  in  a  grebe.  Their  effect  is  that  the  bird  is  able 
to  tread  on  the  lightly- compacted  snow  without  sinking  in. 
It  might  be  interesting  to  test  experimentally  whether 
some  artificial  stimulus,  such  as  damp  ground,  would  serve 
to  induce  the  extra  integumentary  growth  at  some  other 
season  than  winter.  In  regard  to  the  simple  mechanism 
of  extra  lateral  plates,  Dr.  Clark  calls  attention  to  a  very 
interesting  point — a  quaint  structural  analogy.  A  figure 
of  the  Ruffed  Grouse's  toe  in  winter  is  very  much  the  same 
as  a  figure  of  the  arm  of  some  of  the  Crinoids  or  feather- 
stars  from  the  Deep  Sea.  Two  rows  of  supplementary 
plates  occur  on  each  side  of  the  median  row,  and  the  mean- 
ing of  the  adaptation  is  to  increase  the  receptive  surface 
on  which  the  shower  of  minute  dead  organisms  is  caught. 
Thus  we  have  convergent  adaptation  in  two  creatures  almost 


522 


THE  WONDER  OF  LIFE 


literally  as  far 
as  the  poles 
apart ! 

Extraordin- 
ary Egg -carry- 
ing Adaptation 
in  a  Fish. — In 
one  of  the  rivers 
of  New  Guinea 
the  explorer, 
Lorentz,  found  a 
remarkable  fish, 
Kurtus  gulliveri, 
whose  parental 
care  has  been 
described  by 
Prof.  Max 
Weber.  In  the 
mature  male  a 
bony  process  on 
the  back  of  the 
skull  grows  for- 
wards and  down- 
wards like  a  bent 
little  finger,  and 
forms  a  ring  or 
'  eye '.  In  this, 
somehow  or 
other,  a  wreath 
of  eggs  is  at- 

FIQ.  82.— Head  of  Kurtus.   (After  Weber.)    The      t  a  C  h  6  d.     Each 
upper  figure  shows   the   bony   hook.    The 
lower  figure  shows  the  bunch  of  eggs. 


has  an  en- 


THE  WONDER  OF  LIFE  523 

velope  made  of  coiled  filaments ;  these  unwind  when  the 
eggs  are  laid,  and  are  over  a  hundred  in  number.  The 
filaments  unite  into  strings,  and  these  into  a  cylindrical 
band.  Thus  the  eggs  are  bound  together,  forming  a  twin 
cluster  like  a  double  bunch  of  onions.  The  connecting 
band  passes  through  the  bony  ring  and  the  male  goes  about 
carrying  the  eggs  effectively  fastened  on  the  top  of  his 
head.  The  details  of  the  curious  attaching  filaments 
which  fasten  the  eggs  together  have  been  recently  studied 
by  Prof.  F.  Guitel,  who  compares  them  with  those  of 
another  fish,  Clinus  argentatus.  The  adaptation  is  very 
remarkable,  and  one  would  like  to  know  more  in  regard 
to  the  manner  in  which  the  eggs  come  to  be  fastened  to 
the  bony  ring. 

Egg -Eating  Snake. — A  remarkable  structural  adapta- 
tion associated  with  a  remarkable  habit  is  to  be  seen  in  the 
African  egg-eating  snake,  Dasypeltis  scabra,  a  weak-bodied 
creature  less  than  a  yard  in  length  which  is  able  to  swallow 
birds'  eggs  three  times  the  diameter  of  the  thickest  part  of 
its  body.  The  jaws  are  almost  toothless,  but  a  few  pos- 
terior teeth  are  present  which  serve  to  grip  the  egg.  There 
is  the  usual  alternate  gripping  and  muscular  engulfing,  and 
the  intact  egg  slips  into  the  gullet.  It  is  then  met  by  the 
sharp  points  of  the  inferior  spines  of  a  number  of  the  verte- 
brae, which  project  into  the  gullet,  and  cut  the  egg-shells. 
It  is  said  that  they  are  actually  tipped  with  enamel.  The 
result  of  the  structural  adaptation  is  that  none  of  the  precious 
egg  is  wasted.  Mr.  Ditmars,  the  curator  of  reptiles  at  the 
Zoological  Park  in  New  York,  who  has  a  wide  experience 
of  living  snakes,  says  that  the  empty  egg-shells  are  always 
returned,  and  that  this  habit  is  quite  unique.  Many  snakes 
eat  eggs,  but  they  break  the  shells  in  a  rough  and  ready 


524  THE  WONDER  OF  LIFE 

way  by  pressing  their  throats  against  the  ground,  and  in 
these  cases  the  fragments  of  shell  pass  down  into  the 
stomach  and  are  dissolved  away.  One  would  like  to  know 
more  about  an  Indian  snake,  Elachistodon  westermanni, 
which  has  a  structural  peculiarity  like  that  seen  in  Dasy- 
petiis,  but  there  does  not  seem  to  be  any  certainty  as  to 
how  it  uses  it.  As  the  Indian  snake  belongs  to  a  different 
group  the  occurrence  of  a  similar  peculiarity  of  structure 
is  very  interesting,  and  the  interest  would  be  enhanced 
if  there  is  also  an  egg-eating  habit. 

Aristotle's  Lantern. — Commanding  our  admiration 
as  a  piece  of  mechanism  which  can  discharge  several  differ- 
ent functions  is  '  Aristotle's  lantern '  which  surrounds  the 
beginning  of  the  food-canal  in  the  '  regular  '  sea-urchins. 
Aristotle  saw  it  more  than  two  thousand  years  ago — a  neat 
contrivance  with  five  continually  growing  teeth  in  five 
sockets  which  are  united  by  *  braces  '  and  '  compasses  ' 
and  swayed  about  by  strong  muscles  attached  to  five 
'  standards '  on  the  test.  It  is  capable  of  rhythmic  move- 
ment which  helps  in  mastication,  in  boring,  in  respiration, 
and  perhaps  in  keeping  up  a  certain  turgescence  in  various 
internal  cavities  of  the  body  of  the  sea-urchin.  But  perhaps 
the  most  remarkable  thing  about  the  lantern  is  that  dis- 
covered by  Dr.  J.  F.  Gemmill :  it  is  an  organ  of  locomo- 
tion in  certain  conditions,  and  acts  as  an  auxiliary  to  the 
suctorial  tube-feet  and  the  spines.  The  sea-urchin  can 
stumble  along  on  the  tips  of  its  teeth — which  seems  a  most 
extraordinary  statement  to  make.  In  each  step  the  urchin 
is  raised  on  the  tips  of  the  teeth  and  a  forward  impulse 
is  given,  (a)  by  strong  pushing  or  poling  on  the  part  of  the 
lantern,  (6)  by  similar  but  usually  less  effective  pushing 
on  the  part  of  the  spines,  and  (c)  after  a  certain  stage, 


THE  WONDER  OF  LIFE  525 

by  the  influence  of  gravity.  The  lantern  is  then  retracted 
and  the  teeth  swing  forward  into  position  for  initiating  a 
new  lurch. 

Eyes  that  shine  at  Night. — Every  one  knows  the 
gleam  of  a  cat's  eyes  when  a  light  catches  them  in  the 
darkness.  This  appears  to  be  due  to  reflection  from  a 
layer  behind  the  retina  called  the  choroid  tapetum.  This 
layer  includes  numerous  flat  cells  packed  with  crystalloid 
bodies  which  act  like  a  mirror.  In  some  beetles  and  moths 
the  eyes  shine  like  rubies  when  they  are  obliquely  illumined 
at  night.  Prof.  Bugnion  has  recently  studied  the  eyes  of 
one  of  the  hawk-moths,  Sphinx  euphorbias,  and  finds 
that  the  retina  is  very  thick  and  infiltrated  with  a  rose- 
coloured  pigment,  '  erythropsin.'  Part  of  the  retina 
forms  a  tapetum,  and  the  reflection  is  due  to  a  network  of 
silvery  air- tubes  or  tracheae,  helped  to  some  extent  by 
movement  of  the  retinal  pigment.  It  is  probable  that  the 
reflection  of  the  light  rays  from  the  tapetum  is  advan- 
tageous, since  the  visual  cells  are  thus  affected  twice 
instead  of  once. 

The  Chick's  Egg -Tooth  .—An  adaptation  that  gives 
one  pause  is  the  '  egg-tooth  '  found  at  the  tip  of  the  bill  in 
many  young  birds,  and  used  by  them  to  break  a  way  through 
the  imprisoning  egg-shell.  It  is  a  hard  thickening  of  horn 
and  lime  at  the  tip  of  the  bill,  and  since  it  develops  before 
the  horny  ensheathment  of  the  beak  it  may  be  a  residue 
of  a  very  ancient  scaly  armature  in  Reptilian  ancestors  of 
birds.  Be  this  as  it  may,  the  instrument  is  an  effective 
one,  and  it  is  used  only  once  !  What  happens  is  this  : 
the  young  bird  ready  to  be  hatched  thrusts  its  beak  into 
the  air-chamber  that  forms  at  the  broad  end  of  the  egg ; 
air  rushes  down  the  nostrils  and  fills  the  lungs  for  the  first 


526  THE  WONDER  OF  LIFE 

time  ;  in  the  exhilaration  of  this  first  breath  the  unhatched 
bird  knocks  vigorously  at  the  shell  and  breaks  open  the 
prison  doors.  After  a  few  days,  in  most  cases,  the  egg- 
tooth,  having  done  its  work,  falls  off — a  well-adapted 
instrument  that  functions  only  once. 

But  there  is  a  further  detail  which  is  of  much  interest. 
The  bill  and  its  egg-tooth  are  only  the  instruments,  what 
about  the  musculature  which  works  these  ?  Professor  Franz 
Keibel  has  inquired  into  this  in  the  case  of  the  unhatched 
chick  and  duckling.  He  finds  that  the  work  is  done  by  a 
muscle  called  the  musculus  complexus,  and  that  it  is  very 
markedly  hypertrophied  for  some  time  before  hatching. 
On  the  tenth  day  after  hatching,  it  shows  no  peculiarity. 
Here  then  we  have  a  signal  instance  of  the  way  in  which 
development  proceeds  as  if  it  were  working  with  a  purpose. 
How  comes  that  musculus  complexus  to  be  temporarily 
exaggerated  in  strength,  in  relation  to  the  breaking  of  the 
egg-shell — an  action  which  only  occurs  once  in  each  genera- 
tion ? 

Similar  egg-openers  are  well  known  among  insects.  Thus, 
in  the  embryo  of  a  Bug,  Palomena  dissimilis,  described  by 
Heymons,  there  is  on  the  top  of  the  head  a  T-shaped 
chitinous  ridge  with  a  minute  apical  tooth.  This  curious 
apparatus  is  used  to  force  open  the  lid  of  the  egg.  When  the 
young  insect  creeps  out  of  the  egg-envelope,  it  moults  and 
loses  its  egg-opener.  Thus  we  have  another  example 
of  a  structure  which  functions  only  once  in  a  life- time. 

Before  Birth. — There  is  something  very  striking  in 
adaptations  before  birth — in  fitnesses  which  occur  while  the 
creature  is  still  at  its  vita  minima  and  very  inert.  Mr. 
T.  Southwell  finds  a  good  example  in  the  young  of  the  saw- 
fish (Pristis  cuspidatus).  He  dissected  a  large  female 


THE  WONDER  OF  LIFE 


527 


fifteen  and  a  half  feet  long,  and  found  twenty-three  em- 
bryos in  the  oviducts.  As  each  of  these  was  about  fourteen 
inches  long,  including  the  toothed  saw  of  five  inches,  one 
naturally  becomes  curious  as  to  the  relation  of  the  weapon 
to  the  wall  of  the  oviduct.  Mr.  Southwell  found  that  the 
teeth  of  the  saw  were  '  entirely 
covered  by  a  transparent  carti- 
laginous tissue,  which  of  neces- 
sity must  disappear  later.' 

Every  one  who  lives  on  the 
coast  is  familiar  with  the  egg- 
cases  of  skate  and  dogfish,  the 
so  -  called  mermaid's  purses. 
These  are  quadrangular  sacs 
with  a  long  tendril  at  each  of 
the  corners  ;  they  are  made  of 
jets  or  fluid  filaments  of  keratin 
which  are  secreted  by  a  gland  in 
the  oviduct  and  coalesce  into  a 
flexible  egg-case.  There  are  no 
living  cells  in  the  egg-case  itself  ; 
it  encloses  the  large  egg-cell  laden 
with  yolk  and  floating  in  albu- 
men or  white  of  egg.  When  the 
egg  is  liberated  from  the  mother- 
fish,  the  tendrils  writhe  automa- 
tically in  the  water  and  twine 

round  sea-weed  on  the  floor  of  the  sea  in  the  shallow-water 
area.  Thus  the  eggs  are  saved  from  being  smothered  in 
the  drifting  mud,  and  the  developing  embryos  within  are 
gently  rocked,  and  thus  the  better  aerated,  by  movements 
in  the  water.  But  how  is  the  embryo  to  escape  from  its 


FIG.  83. — Mermaid's  Purse, 
or  horny  egg-case  of 
dogfish,  with  attach- 
ing tendrils. 


528  THE  WONDER  OF  LIFE 

closed  cradle  ?  It  appears  that  at  the  time  of  hatching 
there  is  a  secretion  from  the  embryo  which  acts  as  a  solvent 
on  a  weak  seam  at  one  end  of  the  mermaid's  purse.  The 
end  gapes,  and  the  miniature  skate  or  dogfish  works  its 
way  out.  Now  it  is  interesting  to  find  a  parallel  adaptation 
in  the  far-separated  bony  fishes,  where  there  is  no  egg- 
shell, but  only  a  firm  shell-membrane.  Both  in  the  trout 
(Trutta  fario)  and  in  the  goldfish  (Carassius  auratus) 
Wintrebert  has  found  that  the  unicellular  glands  of  the 
embryo's  skin  secrete  before  hatching  a  '  peri-embryonic 
fluid '  which  has  a  digestive  action  on  the  shell- membrane. 
It  becomes  more  delicate  and  finally  almost  like  wet  paper, 
being  readily  broken  without  any  voluntary  movement 
on  the  part  of  the  embryo-fish. 

A  Difficult  Case. — It  must  be  admitted  that  some 
adaptations  are  so  remarkable  that  it  is  very  difficult  to 
resist  the  intellectual  temptation  of  supposing  that  they 
arose  in  direct  relation  to  the  peculiar  conditions.  Let  us 
state  the  case  in  the  words  of  a  naturalist  who  believes 
that  we  are  warranted  in  making  the  supposition  which 
seems  to  us  at  present  illegitimate. 

'  There  is  a  fish  ',  Mr.  J.  T.  Cunningham  writes,  '  which 
has  its  eyes  in  a  very  remarkable  condition.  Spectacles 
for  human  eyes  are  sometimes  made,  in  which  the  upper 
half  has  a  curvature  different  from  that  of  the  lower.  The 
fish  to  which  I  refer,  the  Anabkps,  which  lives  in  the 
estuaries  of  Brazil  and  Guiana,  does  not  wear  spectacles, 
but  actually  has  its  eyes  made  in  two  parts,  the  upper 
half  of  the  lens  having  a  different  curvature  from  that  of 
the  lower.  The  pupil  is  also  divided  into  two  by  prolonga- 
tions from  the  iris.  This  fish  is  in  the  habit  of  swimming 
at  the  surface  with  its  eyes  half  out  of  water ;  the  upper 


THE  WONDER  OF  LIFE  529 

half  of  the  eye  is  adapted  for  vision  in  air ;  the  lower 
half  for  vision  under  water.  Now,  however  various  the 
individual  variations  in  fishes'  eyes,  there  is  no  evidence 
that  variations,  which  could  by  selection  give  rise  to  this 
curious  condition,  occur  in  other  species  of  fish.  It  seems 
to  me  that  we  have  no  reason  to  suppose  that  the  required 
variations  ever  occurred  until  the  ancestors  of  Anableps 
took  to  swimming  with  their  eyes  half  out  of  water.  A 
similar  argument  applies  to  many  other  cases  of  special 
adaptation,  and  the  logical  conclusion  is  that  the  habits 
and  conditions  determined  the  modification'. 

This  is  admirably  put  and  the  difficulty  is  great ;  but  it 
should  be  noted  that  there  has  been  very  little  investiga- 
tion of  the  variations  in  the  eyes  of  fishes,  that  we  have 
very  little  warrant  for  supposing  that  such  a  remarkable 
change  in  the  lens  could  arise  as  the  direct  result  of  the 
peculiar  habits  and  conditions,  and  third,  that  it  is  possible 
that  the  fish  took  to  its  peculiar  mode  of  surface  swimming 
because  its  peculiar  eyes  were  suited  to  that  habit. 

Similar  Structures  put  to  Diverse  Uses. — Our  idea  of 
adaptability  may  be  enriched  if  we  consider  how  the  same 
structure  is  utilized  for  all  sorts  of  different  results.  Let  us 
take  a  series  of  glands,  for  instance,  which,  though  not 
quite  homologous,  are  in  a  general  way  similar — pouring 
a  secreted  juice  into  the  mouth  cavity.  In  a  leech  the 
secretion  keeps  the  ingested  blood  from  coagulating,  so 
that  it  remains  more  usable  in  the  crop  ;  in  some  marine 
Gasteropods  it  contains  dilute  sulphuric  acid  which  seems 
to  be  of  use  in  dissolving  the  carbonate  of  lime,  say  in  a 
starfish's  armour ;  in  some  cuttlefishes,  such  as  Eledone 
moschata,  it  has  a  rapid  paralyzing  effect  on  the  nervous 
system  of  crabs  which  form  an  important  part  of  the  diet ; 

MM 


530  THE  WONDER  OF  LIFE 

in  the  sea-swift  (Collocallia)  it  forms,  when  it  solidifies 
against  the  rock,  the  well-known  '  edible  bird's  nest '; 
in  the  ant-eater  it  moistens  the  worm-like  insect- catching 
tongue  ;  and  in  the  great  majority  of  cases  from  snail  to 
man  it  contains  a  diastatic  ferment  which  changes  the  solid 
starch  of  the  food  into  fluid  and  diffusible  sugar.  We  have 
given  only  a  few  instances  of  the  extraordinary  gamut  of 
function  exhibited  by  glands  which  might  all  be  called 
'  salivary '. 

Some  Functional  Adaptations. — One  of  the  most 
important  of  functional  adaptations  is  that  by  which 
birds  and  mammals  (the  so-called  warm-blooded  animals) 
are  able  to  keep  the  temperature  of  the  body  approxi- 
mately constant.  A  healthy  man  may  '  feel  very  warm  ' 
or  '  feel  very  cold ',  but  his  temperature  varies  very  little 
from  the  normal  37°  C.  or  98  -4°  F.,  year  in,  year  out,  or 
from  the  Poles  to  Equator.  A  bird  may  fly  in  a  very  short 
time,  perhaps  in  a  couple  of  days,  from  North  Africa  to 
within  the  Arctic  circle,  but  there  is  no  reason  to  believe 
that  its  body-temperature  will  change  at  all.  This  keep- 
ing of  a  constant  temperature  is  restricted  to  Birds  and 
Mammals,  which  are  therefore  called  homoiothermal  or 
stenothermal. 

The  problem  is  to  regulate  the  production  of  heat  to  the 
loss  of  heat,  and  it  is  solved  in  Birds  and  Mammals  by  a 
special  adaptation  of  the  nervous  system.  Most  of  the 
heat  that  is  lost  from  the  body  is  lost  from  the  skin  ;  as 
the  skin  gets  cold  nervous  messages  travel  inwards  to  the 
central  nervous  system,  and  reflex  answers  come  out  com- 
manding the  skin  blood-vessels  to  contract  and  command- 
ing the  muscles  to  produce  more  heat.  The  contracting 
of  the  skin  blood-vessels  lessens  the  flow  in  the  skin,  and 


THE  WONDER  OF  LIFE  531 

thus  lessens  the  loss,  while  the  '  toning  up  '  of  the  muscles 
increases  the  supply.  Shivering  is  the  attempt  of  the 
muscles  to  '  tone  up  '. 

It  is  very  interesting  to  consider  some  of  the  exceptions. 
In  the  case  of  many  young  birds  and  mammals,  a  short 
exposure  to  cold  is  fatal,  because  the  thermotaxis  or  heat- 
regulating  arrangement  has  not  yet  been  established.  In 
the  egg-laying  Mammals — the  duckmole  and  the  spiny 
ant-eater — there  is  an  extraordinary  range  of  temperature, 
which  is  what  one  might  expect  in  relative  primitive  types 
with  a  good  deal  of  the  reptile  about  them  still.  In  hiber- 
nating Mammals  like  the  hedgehog  and  the  dormouse,  the 
heat-regulating  arrangement  has  gone  out  of  gear,  and  the 
animal  becomes  colder  and  colder  as  the  external  tem- 
perature falls. 

But  the  most  familiar  exception — all  too  familiar — is 
fever,  which  occurs  when  the  fine  balancing  adjustment 
has  been  put  out  of  gear  by  poisoning,  or  when  the  con- 
ditions of  heat-production  or  heat-loss  are  such  that  the 
normal  arrangements  cannot  cope  with  them.  There  may 
be  too  much  production  of  heat  as  in  pneumonia,  or  too 
little  loss  as  in  typhoid.  If  the  temperature  of  the  blood 
exceed  a  certain  limit,  the  nerve-cells  are  fatally  injured  as 
in  '  sunstroke  '.  It  must  be  noted,  as  Professor  Fraser 
Harris  points  out,  that  while  fever  (pyrexia)  is  the  upsetting 
of  thermotaxis,  the  disturbance  of  the  beautiful  thermal 
balance,  it  is  not  now  regarded  as  a  wholly  bad  thing  to 
be  reduced  at  any  cost.  In  a  luminous  article  he  says  : — 

'  Fever  is  to-day  regarded  by  physicians  in  a  totally 
different  light  from  what  it  was  even  a  few  years  ago — in 
itself  a  wholly  bad  thing  to  be  reduced  at  any  cost.  The 
increased  heat-production  is  looked  on  as  a  reaction  on  the 


532  THE  WONDER  OF  LIFE 

part  of  the  living  cells  to  the  noxious  stimulus  of  the  micro- 
organism or  its  soluble  poison,  a  response  of  a  protective 
nature  rather  than  of  any  other  kind.  Hence  the  indis- 
criminate lowering  of  the  temperature  by  drugs  (anti- 
pyretics) is  not  now  nearly  so  common  as  it  used  to  be.  It 
is  recognized  as  possible  that  the  increase  of  heat  (fever) 
may  be  evidence  of  sufficient  vitality  on  the  part  of  the 
living  protoplasm  to  withstand  the  assaults  of  the  infective 
agents,  the  increased  heat  being  the  biophysical  response 
to  the  micro-organic  insults '. 

It  is  a  familiar  fact  that  living  at  a  high  altitude  puts  a 
strain  on  the  heart,  which  has  more  work  to  do.  Some 
people  cannot  live  above  a  certain  level.  In  this  con- 
nection it  is  interesting  to  refer  to  a  careful  comparison 
made  by  Strohl  of  ptarmigan  from  high  altitudes  and  willow- 
grouse  from  the  plains.  He  found  that  in  the  ptarmigan, 
even  in  the  young  bird,  the  right  ventricle  of  the  heart  is 
very  distinctly  stronger  than  in  the  willow-grouse.  This 
seems  clearly  to  indicate  a  specific  adaptation  of  the  heart 
to  the  difference  of  habitat. 

One  of  the  subtlest  of  adaptations  is  immunity  to  the 
poison  of  some  enemy.  Thus  in  some  parts  of  Europe  there 
is  an  intrepid  little  Rodent,  the  lerot  (Eliomys  nitela),  a 
relative  of  the  dormouse,  which  has  pluck  enough  to  fight 
with  vipers,  and  G.  Billard  has  shown  that  it  is  immune 
to  their  venom.  A  similar  immunity  to  snake  poison  is 
possessed  by  the  mongoose,  the  pig,  and  the  hedgehog. 
And  as  to  the  last,  Dr.  Strubell  has  shown  that  it  is 
relatively  immune  to  the  toxins  of  diphtheria  and  tetanus. 
It  is  likely  enough  that  the  hedgehog  has  a  special  anti- 
toxin which  counteracts  the  toxin  of  snakes,  but  it  is 
difficult  to  understand  what  is  meant  by  its  indifference  to 


THE  WONDER  OF  LIFE  533 

diphtheria  and  tetanus.  Perhaps  it  is  lacking  in  appropriate 
physiological  susceptibility  to  these  diseases,  without 
having  any  special  anti-toxin  against  them. 

It  is  in  human  nature  to  find  satisfaction  in  fitness,  and 
not  for  practical  reasons  only,  but  because  when  things 
'  fit '  we  feel  convinced  of  their  rationality.  It  gave  re- 
assurance to  the  old  lady  to  discover  that  so  many  great 
rivers  flowed  past  so  many  great  towns,  for  that  was  as 
it  should  be ;  and  it  has  often  been  pointed  out  that  the 
length  of  the  day  is  physiologically  well  adapted  to  the 
average  man's  capacity  for  work  !  In  his  famous  Bridge- 
water  Treatise  (1834)  Whewell  showed  in  detail  how  the 
constitution  of  the  world — from  the  length  of  the  year 
to  the  magnitude  of  the  ocean,  from  the  properties  of  water 
to  those  of  the  atmosphere — was  admirably  fitted  for  the 
support  of  the  vegetable  and  animal  life  which  the  earth 
contains.  And  from  of  old  it  has  been  the  delight  of 
naturalists  to  discover  the  adaptations  with  which  organic 
nature  abounds. 

Some  of  those  which  we  have  been  considering  seem 
almost  magical  in  their  intricacy  and  subtlety ;  but  most 
intellectual  combatants  admit  that  Darwinism  has  supplied 
a  partially  adequate  formula  for  their  coming-to-be.  The 
organism  is  always  varying,  always  experimenting — and 
these  variations  or  experiments  (which  we  are  still  only 
beginning  to  study)  form  the  raw  materials  of  organic 
progress.  They  are  subjected  to  Nature's  sifting  and 
singling,  pruning  and  favouring  ('  Natural  Selection  in  the 
Struggle  for  Existence '),  and  the  result  is  the  establish- 
ment of  the  adaptations  we  justly  admire.  The  magicalness 
has  gone ;  the  rationality  is  more  apparent  than  ever. 
And  if  we  can  more  or  less  clearly  see  how  individual 


534  THE  WONDER  OF  LIFE 

adaptations  may  have  been  wrought  out,  this  does  not 
lessen  the  wonder  of  that  variability  that  supplies  the  raw 
material. 

Colour  Adaptations. — There  is  great  wealth  of  colouring 
in  the  animal  kingdom.  Humming-birds,  tropical  fishes, 
mollusc-shells,  butterflies,  starfishes,  and  sea-anemones 
immediately  occur  to  one,  and  it  would  be  easy  to  mention 
a  hundred  gorgeous  examples.  The  colour  is  partly  due  to 
pigmentary  substances  made  by  the  animals ;  partly  to 
the  physical  structure  of  the  surface — e.g.  the  occurrence 
of  thin  lamellae  or  very  delicate  sculpturings  which  cause 
interference  of  light ;  and  partly  to  a  combination  of  pig- 
ment and  some  peculiar  physical  structure.  The  redness 
of  the  blood  is  due  to  a  pigment — haemoglobin ;  the 
iridescence  of  many  a  shell  is  wholly  due  to  the  physical 
structure;  the  coloration  of  a  peacock's  feather  is  due 
to  a  combination  of  the  two  kinds. 

It  may  be  noted,  for  the  sake  of  completeness,  that 
some  animals  owe  their  colour  to  other  organisms  which 
live  in  association  or  partnership  with  them.  Thus  the 
common  green  Hydra  is  green  because  of  minute  partner 
Algae  which  live  within  its  transparent  cells.  And  at  the 
other  end  of  the  scale  we  find  that  the  shaggy  S.  American 
tree-sloth  (Bradypus)  is  greenish,  because  of  minute  Algae 
that,  strangely  enough,  find  a  living  on  its  rough  hair. 

In  the  simple  marine  worm,  Convoluta  roscoffensis,  so 
carefully  studied  by  Professors  Keeble  and  Gamble,  the 
green  colour  is  due  to  a  unicellular  Alga  which  lives  in  part- 
nership with  the  cells  of  the  worm's  body.  The  newly - 
hatched  worm  is  colourless,  and  has  to  be  infected  from  the 
sea- water  or  from  the  egg-capsules  on  which  the  Alga  habitu- 
ally settles.  A  curious  point  is  that  the  green  cells  taken 


THE  WONDER  OF  LIFE  535 

from  an  adult  Convoluta  cannot  live  independently,  and  yet 
we  know  that  the  Alga  lives  freely  in  the  water.  The  in- 
vestigators have  shown  that  this  is  due  to  the  fact  that  in 
association  with  the  worm  the  Algoid  cells  suffer  degenera- 
tion of  their  nucleus.  Thus  the  Alga  becomes  dependent  on 
its  partner,  which  in  turn  becomes  dependent  on  it,  for  in 
course  of  time  the  Convoluta  ceases  to  take  in  food,  relying 
upon  the  materials  worked-up  by  its  partner. 

It  should  also  be  noticed  that  some  animals  owe  their 
colour  directly  to  their  food.  Thus  some  caterpillars  are 
green  because  of  the  chlorophyll  of  the  leaves  they  eat ; 
and  some  sea-slugs  appear  to  borrow  the  pigment  of  the 
sponges  they  browse  on. 

If  we  rank  whiteness  as  a  colour,  it  must  be  regarded  as 
structural,  for  it  is  usually  due  either  to  minute  gas-bubbles  {, 
in  the  cells,  as  in  white  hair  and  feathers,  or  to  minute 
crystalline  spangles,  as  in  many  silvery  fishes.     According 
to  Metschnikoff,  the  whitening  of  hairs  and  feathers  inj 
winter  is  in  certain  cases  due  to  the  activity  of  phagocytes^-* 
which  transport  the  pigment  into  the  skin.     He  made 
observations  on  the  Mountain  Hare  (Lepus  variabilis),  on 
the  Willow  Grouse    (Lagopus  albus),   on  the  ptarmigan 
(Lagopus  alpinus),  and  on  a  hen  which  began  to  turn  white, 
and  found  the  so-called  '  chromophagous '  cells  actively 
at  work. 

As  to  the  form  in  which  pigment  occurs  in  animals, 
there  is  great  diversity.     It  may  be  precipitated  in  a  non-  - 
living  layer,  like  the  zoonerythrin  in  the  cuticle  of  crabs 
and  lobsters,  shrimps  and  prawns  ;  it  may  be  in  the  form  of  • 
minute  granules  in  a  thick  fluid,  as  in  the  sepia  of  cuttle- 
fishes ;  it  may  be  a  solid  mass,  like  the  cochineal  of  coccus  • 
insects ;    it  may  be  in  the  cells  of  the  blood,  as  in  Verte- 


536  THE  WONDER  OF 

brates,  or  in  the  fluid  of  the  blood,  as  in  earthworms ;  it 

»••»  may  be  in  the  form  of  coloured  spicules  or  calcareous 

deposits,  as  in  Alcyonarian  corals ;    it  may  be  in  special 

x-:  cells  which  often  show  considerable  activity — the  chroma- 

tophores  (see  Fig.  87). 

Primary  Significance  of  Pigments. — There  have  been 
relatively  few  important  inquiries  into  the  physiological 
significance  of  pigments,  which  is  a  very  difficult  problem ; 
but  it  may  be  said  that  some  pigmented  substances 
are  of  the  nature  of  waste-products,  like  the  green  guanin 
in  a  lobster's  kidney,  or  the  sulphur-yellow  in  the  wings 
of  some  butterflies,  or  the  sepia  of  the  cuttlefish ;  that 
others  are  of  the  nature  of  reserve  products,  like  the  carmine 
which  accumulates  in  the  body  of  the  female  cochineal 
insect ;  that  others  are  simply  indifferent  by-products  of  the 
metabolism.  That  pigments  need  not  be  useful  as  such 
is  quite  plain  when  we  remember  that  the  internal  organs 
of  many  animals  are  brightly  coloured.  Thus  the  gonads 
of  some  starfishes  and  sea-cucumbers  are  brilliant. 

Primary  Significance  of  Structural  Coloration. — 
The  cross  bars,  the  concentric  lines,  the  zoned  structure, 
and  the  superposition  of  very  thin  lamellae  produce  inter- 
ference colours,  but  what  is  their  primary  significance  ? 
The  answer  must  be,  that  they  are  the  ripple-marks  of 
growth ;  they  are  expressions  of  the  fact  that  growth  is 
rhythmic,  not  continuous.  The  familiar  concentric  lines  on 
the  stem  of  a  tree  express  the  difference  between  the 
summer  and  the  winter  wood  ;  the  lines  on  the  surface  of 
a  shell  are  indices  of  periods  of  growth  punctuated  by 
times  of  rest. 

As  a  further  illustration  of  the  idea  towards  which  we  are 
groping — that  many  structural  features  are  just,  as  it  were, 


FlG.  84. — Head  of  Two- Wattled  Cassowary  (Casuarius  bicaruncu- 
latus).  (After  a  plate  by  Keulemans  in  the  Hon.  W.  Roths « 
child's  monograph.) 


536  THE  WONDER  OF  LIFE 


brates,  or  iu  the  %m&  oj  the  blood,  as  in  earthworms  ;  it 
may  be  in  the  form  of  coloured  spicules  or  calcareous 
deposits,  as  in  Akwjnarian  corals;  it  may  be  in  special 
cells  which  oft***  *&&*-  considerable  activity  —  the  chroma- 
tophores  (so»-  F;#  *7l 

Primary  S»£*utkAm:e  of  Pigments.  —  There  have  been 

relatively  few-  ^8Bp«>it*nt  inquiries  into  the  physiological 

signifies?  ,  ;  -.4  v:$ir\-.^.-Ar>   which  is  a  very  difficult  problem; 

but   it,   ;,-*.*r  h*    amid   that    some  pigmented  substances 

rti't  t-.f  ?Ko.  'kiittii*  of  waste-products,  like  the  green  guanin 

:  H  toii««**»Vi'  kidney,  or  the  sulphur-yellow  in  the  wings 

^s«*  butt«rfb«s,  «r  the  sepia  of  the  cuttlefish  ;    that 

»  art-  of  ihe  nature  «>f  resent  products,  like  the  carmine 

run  accumulates  ifl  the  bod     of  the  female  cochineal 


c5T  .W  .nbH  9Hl  rri  zitomtin'A  yd 


<>f  tnaj*\  Thus  the  gonads 

'          ,...•-   ^       ;  :.'  'iflt. 

Primary    Si  Coloration.  — 

The  cross  bars,  the  concentric  lines,  the  zoned  structure. 
and  the  super  jK>siuon  of  very  thin  lamellae  produce  inter- 
ference colours,  but  what  is  their  primary  significance  ? 
The  answer  must  be,  that  they  are  the  ripple-marks  ot 
growth  ;    they  are  expressions  of  the  fact  that  growth  j* 
rhythmic,  not  continuous.     The  familiar  concentric  li- 
the stem   of   a  tree  express  the  difference  between  tit* 
summer  and  the  winter  wood  ;   the  lines  on  the  sur 
a  shell  are  indices  of  periods  of  growth  pum. 
times  of  rest. 

As-  ustration  of  the  idea  towards  whi 

structural  features  are  just 


THE  WONDER  OF  LIFE  537 

the  ripple-marks  of  internal  tides  (periodic  or  rhythmical 
changes  in  metabolism  and  growth),  we  may  refer  to  the 
suggestive  observations  of  Eiddle  (1908)  on  fault-bars 
in  feathers.  Fault-bars  are  weak  areas  interrupting  the 
fundamental  barring  of  the  feather,  and  they  appear  to  be 
due  to  malnutrition  or  to  defective  nutrition.  They  may 
be  produced  by  feeding  the  birds  with  Sudan  III,  by 
unwholesome  conditions,  or  by  using  amyl  nitrite  to  reduce  «*>"• 
blood-pressure.  They  are  usually  laid  down  at  night, 
when  the  blood- pressure  is  normally  lower  than  during  the 
day.  The  structurally  weakened  areas  tend  to  be  less 
pigmented,  and  it  has  been  shown  that  the  production 
of  the  dark  (melanin)  pigment  in  feathers  may  show 
quantitative  fluctuations  corresponding  to  changes  in  the 
available  food  supply. 

'  The  reduced  nutrition,  brought  about  daily  by  the 
minimum  blood-pressure  ;  the  disadvantageous  position, 
in  relation  to  the  blood,  of  the  pigment  and  barbule  elements 
of  the  feather  ;  together  with  the  very  rapid  rate  at  which 
feathers  grow,  furnish  the  complex  of  conditions  which 
bring  unfailingly  into  existence  a  fault-bar,  and  to  a  more 
or  less  appreciable  extent  a  light  fundamental  bar,  at 
perfectly  regular  intervals  in  the  entire  length  of  every 
feather  formation.' 

This  is  of  very  great  importance,  for  we  are  here  be- 
ginning to  see  how  an  alternation  in  the  rhythm  of  internal 
processes  may  have  far-reaching  external  results — which 
afford  much  more  than  raw  material  for  Selection  to 
work  on. 

Physiologically  useful  Pigments. — Having  recognized 
that  pigments  occur  in  an  organism  as  waste- products, 
reserve-products,  or  by-products,  and  that  there  need  not 


538  THE  WONDER  OF  LIFE 

be  primarily  any  virtue  in  their  colour,  we  hasten  to  point 
out  that  they  are  often  of  very  great  physiological  value, 
and  that  their  colour,  as  well  as  their  chemical  composition, 
may  be  of  vital  importance.  Speaking  metaphorically, 
we  may  say  that  this  has  been  one  of  the  methods  of  evolu- 
tion to  catch  up  some  quality  which  is  present  for  some 
deep  constitutional  reason,  and  give  it  a  novel  secondary 
value — often  life-saving,  (a)  The  whole  world  of  life 
depends  on  the  green  pigment,  chlorophyll,  which  is 
characteristic  of  plants,  for  it  is  a  condition  of  the  photo- 
synthesis or  upbuilding  of  sugar  and  other  organic  com- 
pounds in  the  leaves  that  the  sunlight  should  reach  the 
living  matter  through  the  screen  of  chlorophyll.  (6)  The 
red  pigment,  haemoglobin,  which  made  its  first  appearance 
(as  far  as  we  can  judge)  in  some  Ribbon- worms  or  Nemer- 
teans,  was  also  a  physiological  discovery  of  the  highest 
importance,  for  its  capacity  of  entering  into  a  loose  union 
with  oxygen,  and  thus  becoming  an  oxygen-carrier,  must 
have  greatly  facilitated  and  improved  the  function  of  res- 
piration. Along  with  haemoglobin,  which  occurs  in  all  Verte- 
brates and  in  some  Invertebrates  (such  as  some  Nemerteans 
and  Annelids),  there  have  to  be  ranked  a  number  of  other 
respiratory  pigments.  One  of  the  commonest  of  these 
among  Invertebrate  animals  is  haemocyanin,  of  a  faint 
bluish  colour.  In  addition  to  transporting  oxygen,  some 
pigments  are  of  great  value  in  storing  it  within  the  body. 
}  e.g.  in  the  muscles,  (c)  Another  use  of  pigment  is  in 
S/  connexion  with  vision,  for  the  dark  pigments  of  the  retina 
}are  continually  undergoing  chemical  change,  and  they 
often  show  remarkable  alterations  in  position.  In  the 
peculiar  condition  known  as  night-blindness  there  appears 
to  be  a  lack  of  the  normal '  visual  purple  '  in  the  retina. 


THE  WONDER  OF  LIFE  539 

(d)  Another  direct  utility  may  be  recognized  in  the  pigmen-\ 
tation  of  the  skin  in  various  animals.     Thus  the   dark/ 
skin  of  some  animals  from  very  warm   countries   and ' 
the  whiteness  of  some  animals   from  very  cold  countries 
may  have  a  direct  physiological  value    to  its  possessor. 
It  appears  that  the  dark  insoluble  melanin  pigments,   as 
in  the  crow  and  negro,  are  protective  against  the  ultra- 
violet rays  of  sunlight.'  A  remarkable  fact  was  observed 
by  Engelmann  in  regard  to  the  peculiar  restless  Algae 
known  as  Oscillatoria.      He  found  that  in  red  light  they  , 
had  a  green  colour,  and  in  green  light  a  red  colour — in  ' 
both  cases  the  physiologically  best  colour. 

Protective  Value  of  Coloration. — Some  of  the  finest 
instances  of  adaptation  are  seen  in  the  way  animals  resemble 
their  habitual  environment.  Shape  and  pose  sometimes 
conspire  with  coloration  to  give  the  animal  a  mantle  of 
invisibility.  Referring  for  details  to  books  on  animal  color- 
ation by  Professor  E.  B.  Poulton  and  Mr.  F.  E.  Beddard, 
we  wish  to  give  a  few  representative  illustrations.  Many 
desert  animals  have  an  isabelline  or  sandy  coloration  that 
renders  them  very  inconspicuous ;  the  fennec  fox  and  the 
gerbille,  the  sand-grouse  and  the  horned  viper  are  good 
examples.  Green  snakes  are  difficult  to  detect  on  the 
trees  and  the  common  shore-crab,  whose  colour  is  variable, 
often  harmonizes  to  a  nicety  with  the  background  of  the 
rock-pool.  In  many  birds  and  mammals,  as  Thayer  has 
well  shown,  a  very  perfect  garment  of  invisibility  is  attained 
in  a  very  simple  way — by  having  the  under  surface  of  the  \ 
body  rather  lighter  than  the  upper  surface. 

The  protectiveness  is  heightened  when  the  animal  is 
like  something  else,  not  in  colour  merely,  but  in  form ; 
and  there  is  no  better  example  than  the  Javanese  butterfly 


540 


THE  WONDER  OF  LIFE 


Kallima,  which  is  conspicuously  coloured  on  the  upper 
surface,  but  becomes  like  a  withered  leaf  when  it  folds 
its  wings  together  and  exposes  the  brown  under  surface 
(Fig.  11).  As  we  have  noted,  the  nervures  on  the  wings  look 

like  the  veins  on  a 
leaf,  and  the  sug- 
gestion of  a  mid- 
rib increases  the 
resemblance. 
Spots  on  the 
wings  look  like 
holes  on  the  leaf, 
and  so  on.  In 
fact,  perfection  is 
attained  by  the 
combination  of  a 
number  of  items. 
Even  the  fact 
that  the  colora- 
tion of  the  under 
surface  and  the 
position  of  spots 
may  vary  a  little 

PIG.   85.— Two    spiders :     I.   Cserostris  mitralis  1S     PernaPs     ad' 
like   a  knot  on  a  twig;    and  II,    Ornitho-  vantag6OUS,since 
scatoides  decipiens,  like   a  bird's   dropping.   , ,      ,     . ,      *     i 
(After  Vinson  and  Pickard-Cambridge.)  tne  butterfly  has 

thus    a    general 

resemblance  to  different  kinds  and  states  of  withered  leaves. 
Protective  colour- resemblance  is  seen  at  its  best  in  cases 
where  the  animal  can  adjust  itself  to  the  coloration  of  the 
surface  on  which  it  is  resting ;  and  there  is  no  better  illus- 
tration than  that  of  plaice  and  other  flat-fishes,  which  are 


THE  WONDER  OF  LIFE 


able  in  a  short  time  to  alter  the 
disposition  of  their  pigment  cells 
so  as  to  become  part  and  parcel  of 
their  background.  The  figures  we 
have  given  show  the  nicety  of  the 
harmonious  adjustment  (Fig.  10). 

Great  care  must  be  exercised 
in  ascribing  protective  value  to 
the  colour- resemblance  between 
an  animal  and  something  else, 
and  each  case  must  be  judged  on 
its  own  merits.  It  must  be  made 
clear,  for  instance,  that  the  re- 
semblance which  conceals  the 
creature  from  us  is  equally  effec- 
tive in  concealing  it  from  its 
natural  enemies.  The  desert  in- 
sect does  not  escape  the  desert 
lizard,  and  the  green  insect  on 
the  twig  is  unhesitatingly  picked 
off  by  the  sharp-eyed  bird  who 
has  made  that  its  business.  Some 
creatures,  like  sea-slugs,  which 
are  often  very  harmonious  with 
their  surroundings,  are  seldom 
eaten  by  anything. 

It  is  satisfactory,  then,  that 
there  are  some  definite  observa- 
tions proving  the  protective  FIG. 
value  in  particular  cases.  With 
silk  threads  Cesnola  tethered 
forty-five  green  praying  mantises 


UM 


86. — A  Venezuelan  insect, 
Umbronia  spinosa,  with 
a  marked  resemblance  to 
a  prickle  on  the  twig  on 
which  it  (UM)  is 
From  a  specimen^ 


542  THE  WONDER  OF  LIFE 

to  green  herbage,  and  sixty-five  of  the  brown  variety 
to  withered  herbage,  and  found  that  the  birds  had 
not  noticed  any  of  them  within  the  seventeen  days  of 
the  experiment.  But  it  was  quite  another  story  when 
he  reversed  the  arrangement.  When  he  put  twenty- 
five  green  ones  among  brown  herbage,  all  were  killed  by 
birds  in  eleven  days,  while  of  forty-five  brown  ones  on 
green  grass,  only  ten  survived  at  the  end  of  seventeen  days. 
Here  we  have  definite  proof  of  a  selective  death-rate, 
definite  proof  of  the  protective  value  of  the  colour-resem- 
blance. And  happily  the  case  does  not  stand  alone. 

In  some  cases  the  colour- resemblance  between  the  animal 
and  its  immediate  environment  has  a  very  simple  explan- 
ation. The  sea-lemon  Archidoris  tuberculata  is  yellow  when 
it  is  eating  the  yellow  sponge  Dendoryx  incrustans  and  red 
when  it  is  eating  the  red  Esperella  cegagrophila.  It  is 
thus  coloured  like  the  sponge  it  is  browsing  on ;  the 
sponge's  colour  has  directly  affected  it.  This  is  an  individ- 
ually acquired  character — a  modification,  and  not  to  be 
confused  with  inborn  colour- changes — which  we  call 
variations.  Whether  the  sea-slug  is  protected  or  not  by 
its  modification,  we  do  not  know,  but  the  point  is  that,  if  it 
should  turn  out  to  be  protected,  the  origin  of  the  protec- 
tion is  obvious. 

Dr.  A.  Ch.  Hollande,  of  Nancy,  reports  a  very  interesting 
case  of  an  insect  apparently  protected  by  its  meals.  The 
flower-buds  of  one  of  the  mountain-mulleins  (Verbascum 
nigrum)  are  pierced  in  autumn  by  the  larva  of  a  Curculionid 
beetle  called  Cionus  olens,  which  feeds  on  the  violet  hairs  of 
the  stamens.  The  violet  vegetable  pigment  (anthocyan) 
eaten  by  the  grub  passes  down  the  food-canal,  and,  in 
the  usual  way,  into  the  blood,  where,  however,  it  has  an 


THE  WONDER  OF  LIFE  543 

uncoloured  form.  It  is  carried  to  the  fatty  bodies  and 
accumulates  there  in  numberless  granulations,  re-assuming 
the  violet  colour,  which  shines  through  the  brownish 
integment  and  makes  the  grub  effectively  harmonious 
with  the  colour  of  the  stamens  amid  which  it  works. 

In  the  case  of  the  Tree-Sloth,  the  green  colour  of  the 
hair  is  due  to  Algse  which  might  grow  elsewhere,  and  as 
there  are  other  instances  of  plants  of  low  degree  growing 
on  living  hairs,  the  Sloth's  case  is  no  particular  puzzle. 
In  Baron  Albert  von  Sack's  Voyage  to  Surinam  (1810) 
there  is  a  surprisingly  early  reference  to  this  peculiar  case 
of  protective  resemblance. 

'  The  colour  and  even  the  shape  of  the  hair  are  much  in 
appearance  like  withered  moss,  and  serve  to  hide  the  animal 
in  the  trees,  but  particularly  when  it  gets  that  orange- 
coloured  spot  between  the  shoulders,  and  lies  close  to  the 
tree ;  it  looks  then  exactly  like  a  piece  of  branch  where 
the  rest  has  been  broken  off,  by  which  the  hunters  are  often 
deceived '. 

Account  must  also  be  taken  of  cases  where  the  particular  \  / 
colour  depends  physiologically  on  that  of  the  surroundings.  T 
Some  caterpillars  have  a  sensitive  period  during  which 
their  colour  or  that  of  the  pupae  is  influenced,  within  certain 
limits,  by  the  surrounding  colour.  This  has  been  proved 
experimentally  by  Professor  Poulton,  Schroder,  and  others. 
How  the  colour  of  the  reflected  light  affects  the  pigmen- 
tation of  the  animal  is  obscure,  but  the  fact  is  certain  in  a 
few  cases,  and  it  is  to  be  associated  with  the  fact,  also 
proved  in  a  few  cases,  that  the  mortality  among  pupae  is 
in  part  dependent  on  the  degree  of  their  inconspicuousness 
against  certain  backgrounds.  It  is  stated  that  the  colour 


544 


THE  WONDER  OF  LIFE 


of  a  shore-crab  is  directly  influenced,  while  the  shell  is 
being  formed  after  a  moult,  by  the  dominant  colour  of  the 
immediate  environment. 

There  can  be  no  doubt  that  certain  colour-reactions 
which  follow  reflexly  and  necessarily  often  look  as  if  they 


FIG.  87. — Much  branched  chromatophore  of  a  prawn,  Praunus  flexuoxua. 
(After  Degner.)  The  pigment  flows  out  along  the  root-like  branches 
or  contracts  centripetally.  The  chromatophore)[seems  to  arise 
from  a  combination  of  cells — a  syncytium. 

should  be  advantageous,  but  it  is  difficult  to  give  direct 
proof  of  this.  One  of  the  prawns,  Palcemon  treillianus 
studied  byFrohlich  (1910)  is  blue  or  green  by  day^when 
its  red  chromatophores  are  strongly  contracted,  and  reddish- 
brown  by  night,  when  the  red  chromatophores  expand. 
When  one  is  put  into  a  white  porcelain  vessel  it  becomes 


THE  WONDER   OF  LIFE  545 

milky  and  translucent ;  the  chromatophores  contract 
greatly,  and  there  is  an  unexplained  turbidity  in  the  cara- 
pace. When  it  is  put  into  a  glass  vessel  and  that  placed 
on  a  mirror,  it  becomes  transparent,  the  maximum  con- 
traction of  chromatophores  occurs.  It  is  easy  to  imagine 
conditions  where  this  milkiness  or  this  transparency  would 
be  very  useful.  On  the  other  hand,  we  read  that  an 
individual  forced  to  jump  loses  its  transparency,  which 
does  not  sound  so  adaptive. 

Professors  Gamble  and  Keeble  have  demonstrated  a 
remarkable  plasticity  in  the  coloration  of  the  vEsop-prawn 
(Hippolyte  varians),  which  may  be  red,  yellow,  blue,  orange, 
olive,  violet,  brown,  green,  and  other  colours.  It  is  born 
without  a  bias,  and  it  takes  on  the  hue  of  its  environment, 
both  when  young  and  adult.  If  it  is  put  in  an  aquarium 
the  sides  and  floor  of  which  are  lined  with  coloured  paper, 
it  takes  on  the  colour  ;  and  it  will  change  from  one  colour 
to  another.  It  seems  to  have  more  plasticity  in  its  color- 
ation than  it  can  possibly  need,  but  it  can  make  itself 
invisible  among  the  bright  colours  of  seaweed. 

In  the  ^Esop- prawn  the  colour  changes  periodically 
with  the  nervous  state  of  the  animal,  according  as  it  is 
sleepy  or  wakeful.  We  venture  to  quote  Professor  Gamble's 
fine  description  (The  Animal  World,  p.  140)  : 

'  The  wakeful  hours  of  Hippolyte  are  hours  of  expansion. 
The  red  and  yellow  pigments  flow  out  in  myriads  of  stars 
or  pigment-cells  ;  and  according  to  the  nature  of  the  back- 
ground, so  is  the  mixture  of  the  pigments  compounded  to 
form  a  close  reproduction  both  of  its  colour  and  its  pattern  : 
brown  on  brown  weed,  green  on  Ulva  or  sea-grass,  red  on 
the  red  Algae,  speckled  on  the  filmy  ones.  A  sweep  of  a 
shrimp  net  detaches  a  battalion  of  these  sleeping  prawns, 

N  N 


546  THE  WONDER  OF  LIFE 

and  if  we  turn  the  motley  into  a  dish  and  give  a  choice  of 
seaweed,  each  variety  after  its  kind  will  select  the  one 
with  which  it  agrees  in  colour,  and  vanish.  At  nightfall, 
Hippolyte,  of  whatever  colour,  changes  to  a  transparent 
azure  blue  ;  its  stolidity  gives  place  to  a  nervous  restless- 
ness ;  at  the  least  tremor  it  leaps  violently  and  often 
swims  actively  from  one  food-plant  to  another.  This  blue 
fit  lasts  till  daybreak,  and  is  then  succeeded  by  the  prawn's 
diurnal  tint.  Thus  the  colour  of  an  animal  may  express 
a  nervous  rhythm '. 

In  many  cases,  both  among  plants  and  animals,  the 
range  of  colour  exhibited  by  one  and  the  same  organism 
is  very  striking,  but  it  has  sometimes  a  very  simple  ex- 
,  .^planation.  There  is  a  colourless  '  chromogen  '  substance, 
j  or  '  mother  of  pigment ',  which  takes  on  different  colours 
according  to  the  amount  of  oxidation  to  which  it  is  sub- 
jected under  the  action  of  a  ferment.  One  of  the  common 
colour- evoking  ferments  is  called  tyrosinase.  The  different 
colours  in  cases  of  this  sort  simply  correspond  to  different 
rates  or  rhythms ;  and  it  is  easy  to  understand  how  this 
or  that  punctuation  might  be  fixed  by  Natural  Selection. 

The  common  sea-slater,  Lygia  oceanica,  has  numerous 
much-branched  black  or  dark  brown  chromatophores  in 
its  epidermis,  which  make  it  inconspicuous  against  a  dark 
background  of  rock.  Tait  has  shown  (1910)  that  if  the 
creature  is  exposed  to  light  in  a  black-painted  dish,  it 
remains  dark,  but  that  if  it  is  exposed  in  a  white  dish  it 
becomes  lighter  in  colour  and  more  transparent,  so  that 
eventually  the  heart  can  be  seen  beating  through  the  skin. 
This  change  is  due  to  a  retraction  of  the  black  chroma- 
tophores, which  also  leaves  certain  white  chromatophores 
more  in  evidence.  When  the  eyes  are  painted  over  with 


THE  WONDER  OF  LIFE  547 

lampblack,  no  change  follows  the  transference  to  a  white 
surface,  which  shows  that  the  external  colour  first  affects 
the  eyes,  then  the  central  nervous  system,  and  then  the 
pigment-cells  in  the  skin. 

It  is  very  instructive  to  compare  the  juvenile  and  the 
adult  coloration.  In  many  young  mammals  and  birds, 
as  Dr.  Chalmers  Mitchell  has  well  shown  in  his  Childhood 
of  Animals,  the  coloration  requires  little  more  than  a 
physiological  interpretation.  The  pigments  are  by- 
products of  the  metabolism  ;  they  are  laid  down  in  agree- 
ment with  the  particulate  character  of  the  skin,  or  they 
may  express  the  rhythms  of  growth — being  laid  down,  for 
instance,  in  concentric  lines  and  cross-bars.  If  this  primi- 
tive coloration  is  not  disadvantageous,  it  will,  of  course 
be  tolerated,  but  the  point  is,  that  it  does  not  require  any 
special  utilitarian  explanation.  It  may,  indeed,  be  quite 
useful — thus  the  spottiness  of  some  young  mammals 
makes  them  very  inconspicuous.  As  the  young  creature 
grows  its  coloration  changes.  The  spots  may  unite  into 
stripes  or  bands,  or  they  may  be  blurred  into  a  monotone. 
Or  it  may  be  that  a  new  pattern  replaces  the  primitive  one ; 
sometimes  of  ruptive  vividness,  so  that  the  natural  outlines 
of  the  animal  are  broken  up  protectively ;  sometimes  of 
startling  and  impressive  brilliance,  such  as  we  see  in  certain 
sex-decorations.  It  is  when  we  pass  to  the  secondary 
coloration,  analysed  out  of  the  primary  as  aniline  dyes 
from  the  coal-tar  residue,  that  we  feel  the  need  of  special 
utilitarian  or  selectionist  interpretations.  And  they  are 
not  lacking ! 

Warning  Coloration. — A  third  use  of  coloration, 
first  expounded  by  Alfred  Eussel  Wallace,  is  as  an  advertise- 
ment on  the  part  of  animals  that  are  unpalatable  or  offensive 


548  THE  WONDER  OF   LIFE 

or  in  some  way  safe.  '  They  require ',  as  Wallace  said, 
'  some  signal  or  danger  flag,  which  shall  serve  as  a  warning 
to  would-be  enemies  not  to  attack  them,  and  they  have 
usually  obtained  this  in  the  form  of  conspicuous  or  brilliant 
coloration,  very  distinct  from  the  protective  tints  of  the 
defenceless  animals  allied  to  them  '.  It  is  satisfactory  that 
this  interpretation  has  been  justified  by  a  number  of 
experiments,  which  go  to  show  that  hungry  animals,  once  or 
twice  duped  by  having  conspicuous  unpalatable  caterpillars 
and  the  like  given  to  them  to  eat,  soon  learn  by  experience 
and  are  aided  in  this  by  the  impressiveness  of  the  colouring. 
Even  in  fishes,  whose  cerebrum  remains  at  a  very  low  level, 
an  association  between  colour  and  a  gustatory  experience 
may  be  established  and  retained.  It  has  to  be  admitted, 
however,  that  in  many  cases  the  experiment  of  offering 
conspicuous  unpalatable  caterpillars  and  the  like  to  hungry 
animals  has  failed  to  confirm  the  theory  of  warning  color- 
ation, so  that  each  case  has  to  be  judged  on  its  own  merits. 
In  some  cases  there  appears  to  be  truth  in  the  interesting 
suggestion  of  Eisig,  that  very  abundant  deposition  of  a 
waste-matter  pigment  may  render  an  animal  at  once 
unpalatable  and  conspicuous. 

This  much  seems  certain,  that  numerous  noxious  or 
aggressive  types,  such  as  wasps,  coral  snakes,  and  skunks, 
are  conspicuously  coloured.  A  familiar  and  plausible 
illustration  may  be  found  in  the  common  salamander 
(Salamandra  maculosa),  which  is  conspicuous  in  its  black 
and  yellow  livery  and  has  a  very  glandular  skin — the 
secretion  of  which  is  perhaps  noxious. 

Recognition -Marks  and  Guide-Marks. — A  fourth 
use  of  coloration  is  to  aid  animals  in  the  rapid  recog- 
nition of  their  kith  and  kin,  and  in  the  rapid  execution  of 


THE  WONDER  OF  LIFE  549 

precise  movements,  such  as  placing  food  in  the  nestling's 
mouth.  It  was  Alfred  Russel  Wallace  who  first  expounded 
the  theory  of  recognition  colours,  bringing  forward  in- 
stances, especially  from  among  deer,  antelopes,  birds,  and 
insects,  of  striking  patches  of  colour  which  may  be  plausibly 
interpreted  as  facilitating  rapid  recognition.  One  of  the 
best  instances  is  also  the  most  familiar — the  rabbit's 
upturned  white  tail.  When  they  are  feeding  in  the  twilight 
and  are  suddenly  alarmed,  safety  may  depend  on  the 
rapidity  with  which  they  reach  the  burrows.  Hesitation 
may  be  quite  fatal,  and  it  does  not  seem  far-fetched  to 
suppose  that  '  the  white,  upturned  tails  of  those  in  front 
serve  as  guides  and  signals  to  those  more  remote  from 
home,  to  the  young  and  the  feeble '.  The  white  stripe 
above  the  springbok's  tail,  which  is  nearly  concealed  when 
the  animal  is  at  rest,  but  very  prominent  when  it  starts  to 
run,  is  probably  another  good  instance. 

In  Mr.  W.  P.  Pycraft's  fine  History  of  Birds,  which  is  a 
rich  treasure-house  for  students  of  adaptations,  attention 
is  called  to  the  bright  colours  sometimes  seen  around  or 
in  the  mouth  of  nestlings  ;  and  the  interpretation  is  offered 
that  they  serve  as  a  guide  to  the  parents  when  feeding  the 
young.  The  inside  of  the  mouth  is  diversely  coloured,  e.g. 
bright  yellow,  as  in  the  thrush,  and  purplish-red,  as  in  the 
chaffinch,  while  in  the  Bearded  Titmouse  it  is  of  '  a  bright 
cornelian  red,  surrounded  by  a  band  of  yellow,  and  relieved 
by  a  double  row  of  white,  glistening,  tooth-like  conical 
processes '.  It  seems  that  the  most  elaborate  oral  decor- 
ations, as  in  the  Gouldian  Weaver-finch  (Poephila  gouldii), 
are  found  in  young  birds  which  are  hatched  in  places  where 
there  is  but  little  light.  Chun  has  noted  that  in  this  bird 
the  brilliant  bodies  at  the  angles  of  the  mouth  of  the  nestling 


550  THE  WONDER  OF  LIFE 

reflect  the  light  like  mirrors  and  are  effective  guide-marks. 

Attractive  Coloration. — A  fifth  use  of  coloration 
is  to  add  to  the  ensemble  of  attractiveness  which  one  sex 
has  for  the  other,  and  which,  by  stimulating  sexual  interest 
and  increasing  sexual  excitement,  makes  pairing  more  effec- 
tive. It  is  usually  the  male  who  is  the  more  decorative  and 
brilliant,  but  there  are  exceptional  cases  of  the  reverse. 
The  tail  of  the  peacock  is  a  masterpiece  in  this  kind  of 
coloration,  and  the  decorativeness  of  male  Birds  of  Para- 
dise and  Lyre-Birds  and  Pheasants  is  hardly  less  transcen- 
dent. The  habits  of  Bower-birds  and  some  other  birds 
which  collect  brightly-coloured  or  shining  objects,  suggest 
that  an  appreciation  of  colour,  as  colour,  is  not  wanting, 
but  in  thinking  of  courtship  coloration  it  is  probably  safer 
not  to  be  too  analytic,  crediting  the  female  bird  with  too 
much  in  the  way  of  particulate  aesthetic  discernment.  It  is 
probably  the  total  impression  of  agility,  beauty,  vigour  and 
other  qualities  which  kindles  or  fans  the  fire  of  sexual 
excitement  in  the  coy  female. 

The  brilliant  coloration  of  the  males  is  in  some  measure 
latent  in  the  females,  as  is  shown  in  cases  where  an  old 
female  bird,  or  one  with  an  abnormal  ovary,  begins  to  put 
on  a  masculine  dress.  The  masculine  characteristics  are, 
as  it  were,  seeds  which  will  not  normally  develop  except 
in  male  soil.  They  are  parts  of  the  inheritance,  but  they 
do  not  start  developing  except  in  appropriate  soil  and  in 
response  to  appropriate  stimulus.  It  has  been  shown 
experimentally  that  the  stimulus,  in  some  cases  at  least, 
is  furnished  by  the  '  hormones  '  or  internal  secretions  of  the 
reproductive  organs  which  are  diffused  by  the  blood  through- 
out the  body  when  the  organism  becomes  adolescent  or 
when  the  breeding  season  sets  in.  It  is  interesting  to  find 


FIG.  88. — Shallow- water  marine  animals  with  bright  colours.  1. 
Elephant's  Tusk  Shell,  Dentalium.  2.  Chiton.  3.  Starfish. 
Echinaster  sepositus,  (After  Ludwig.).  4.  Sea  Cucumber.  5. 
Sea  Anemone,  Actinia  mesembryanthemum.  (After  Andres.) 
6.  Cluster  of  Ascidians.  7.  Small  Cuttlefish,  Sepiola.  (After 
Jatta.) 


550  THE   WONDER  OF  LIFE 

reflect  the  light  like  mirrors  and  are  effective  guide-marks. 
Attractive  Coloration.  A  fifth  use  of  coloration 
is  to  add  to  the  cn&mble  of  attractiveness  which  one  sex 
has  for  the  other,  and  which,  by  stimulating  sexual  interest 
and  increasing  sexual  excitement,  makes  pairing  more  effec- 
tive. It  is  usually  the  male  who  is  the  more  decorative  and 
brilliant,  but  there  are  exceptional  cases  of  the  reverse. 
The  tail  of  the  peacock  is  a  masterpiece  in  this  kind  of 
coloration,  and  the  decora  tiven  ess  of  male  Birds  of  Para- 
dise- and  Lyre-Birds  and  Pheasants  is  hardly  less  transcen- 
dent. The  habits  of  Bower-birds  and  some  other  birds 
.1  .siuolco  fcighd  Hriw  slsopifl^,  afifiMft  ,  •»  J 
./ieihalS  .£  .  nolirO  £  .muilBinsQ  JlaHS  jJeuT 
.<!  ^.ladfriJJDuD  B32  .I1  .(.giwtuJ  tsi\K)  .atrtieoqae  laleBni 


sthetic 

.:•<•  ••••-.  .  beauty,  vigour  and 

other  qualities  fire  of  sexual 

excitement  in  the  coy  femuk:-. 

The  brilliant  coloration  o  sure 

latent  in  the  females,  as  is  shown  in  cases  where  an  old 
female  bird,  or  one  with  an  abnormal  ovary,  begins  to  put 
on  a  masculine  dress.     The  masculine  characteristics  are, 
as  it  were,  seeds  which  will  not  normally  develop  except 
in  male  soil.    They  are  parts  of  the  inheritance,  but  they 
do  not  start  developing  except  in  appropriate  soil  aji 
response   to   appropriate   stimulus.     It  has   been  sh 
experimentally  that  the  stimulus,  in  some  cases  at  1- 
is  furnished  by  the  '  hormones  '  or  internal  secretions  o 
reproductive  organs  which  are  diffused  by  the  blcxx  ; 
out  the  body  when  the  organism  becomes  adoleso* 
when  the  breeding  season  sets  in.     It  is  int»;-- 


THE  WONDER  OF  LIFE  551 

many  cases,  e.g.  pheasants,  in  which  the  brilliant  color- 
ation, which  is  in  most  cases  '  nuptial ',  is  a  constant 
masculine  character. 

In  Summary. — The  point  that  we  wish  to  emphasize 
in  this  brief  survey  of  animal  coloration  is,  that  the  pigment  ! 
substances  are  primarily  waste-products,  reserve-products,  ( 
or  by-products  of  the  animal's  metabolism,  and  that  in  ) 
many  cases  the  colours  have  no  more  significance  for  their 
possessors  than  the  gorgeous  autumnal  tints  of  withering 
leaves  have  for  the  tree — that  is  to  say,  none  !     Similarly, 
the  structural  features  that  cause  iridescence  and  the  like 
are  primarily  the  ripple-marks  of  growth.     Likewise,  in 
many  cases,  it  seems  probable  that  the  colouring  of  special 
parts  of  the  body  is  due  to  particulate  conditions  in  different 
parts.     Just  as  green  vivianite  may  be  deposited  in  the 
bones  of  a  gar-pike,  because  of  certain  physiological  con- 
ditions, so  an  island  on  the  skin,  the  tip  of  an  ear,  the  end 
of  a  tail  may  have  a  special  colouring.     In  many  cases, 
all  theory  apart,  it  is  certain  that  the  pigments  have  come  1 
to  play  an  important  role  in  the  internal  economy  of  the  ( 
body,  as  in  the  case  of  haemoglobin.      From  this  basis, 
however,  we  must  go  on  to  the  further  step,  that  in  the 
course  of  ages  of  variation  and  selection,  certain  arrange- 
ments of  pigmentation  and  markings  have  been  caught  up, 
as  it  were,  into  the  service  of  the  animal's  struggle  for  \ 
existence,  and  utilized,  often  with  extraordinary  subtlety/ 
and  effectiveness,    in    concealment,  in  advertisement,  as; 
aids  in  recognition,  and  as  auxiliaries  in  courtship.     But  * 
to  look  everywhere  for  secondary  utilitarian  justification 
is  quite  gratuitous. 

An  interesting  case  of  coloration  is  found  in  a  sea-urchin, 
Echinus  angulosus,  common  on  South  African  coasts  and 


552  THE  WONDER  OF  LIFE 

elsewhere.  Dr.  Stuart  Thomson  points  out  that  many 
colours  occur  on  different  specimens — purple,  red,  green, 
grey,  intermediate  between  purple  and  grey,  intermediate 
between  green  and  purple,  pink,  lilac,  and  so  on.  The 
coloration  is  variable.  The  investigator  has  tested  various 
utilitarian  interpretations,  and  finds  them  all  untenable. 
The  coloration  is  not  protective,  or  aggressive,  or  for 
warning,  or  connected  with  sex.  Its  meaning  is  to  be 
sought  for  in  the  internal  physiological  processes  (probably 
respiratory  or  excretory)  of  the  animals  themselves.  To 
this  sound  conclusion  we  have  simply  to  add  that  it  is 
conceivable  that  in  the  future  the  coloration  might  be 
caught  up  into  the  service  of  the  sea-urchin's  general  life, 
and  utilized,  let  us  say,  for  protection. 

REGENERATION  OF  LOST  PARTS 

From  ancient  times  something  has  been  known  of  the 
regenerative   capacity  of  living   creatures.     The   pruned 
tree  regrows  its  branches  and  a  small  cutting  can  re-grow 
the    entire    plant.     The    hair 
that  is  shaved  off  soon  grows 
again — sometimes  reproducing 
millions  of  cells  every  day,  and 
the  stag's  antlers  fall  off  and 
are  re -grown  every  year.     But 
it  was  not  till  the  eighteenth 
FIG.  89.-"  Monster"    form  of  century  that  scientific  attention 
Hydra  1grisea,  with   eight  was  focussed  on  the  remarkable 
heads  and  two  bases.    (After    ,     .         T,  ,.         _,,     ,   m 

Roesel  von  Rosenhof.)  facts.     It  was  then  that  Trem- 

bley  discovered  the  freshwater 
polyp  and  called  it  Hydra,  after  the  monster  with  which  Her- 


THE  WONDER  OF  LIFE  553 

cules  contended,  for  he  found  to  his  delight  that  it  could  be 
multiplied  by  being  cut  in  pieces.  It  was  then  that  Spal- 
lanzani  showed  that  the  earthworm  cut  by  the  spade  might 
re-grow  a  new  tail  or  even  a  new  head.  Bonnet  made 
numerous  experiments  on  other  worms  and  thought  out  an 
elaborate  theory.  Reaumur,  with  his  wonted  insight, 
advanced  to  an  almost  modern  position  when  he  pointed 
out  the  advantage  of  the  regenerative  capacity  in  animals 
which  were  in  the  natural  conditions  of  their  life  exposed 
to  frequent  risk  of  breakage  or  wounds. 

Instances  of  Regeneration. — During  the  last  twenty 
years  there  has  been  a  boom  of  experimental  work  bearing 
on  regeneration — chiefly  for  the  reason  that  the  pheno- 
mena throw  light  on  the  physiology  of  development.  Many 
remarkable  facts  have  come  to  light,  of  which  the  following 
are  typical : — half  of  the  highly  differentiated  Infusorian 
Stentor  can  quickly  regenerate  the  missing  half  and  minute 
slices  across  the  cell  can  re-grow  the  whole ;  from  one 
Planarian  worm  six  or  more  may  be  produced  by  cutting 
it  into  pieces  ;  a  starfish  can  re-grow  a  lost  arm,  and  the 
lost  arm  can  complete  a  new  starfish  ;  a  crab  can  re-grow  a 
lost  limb  ;  if  the  eye-bearing  horn  of  a  snail  be  cut  off,  it  is 
regenerated  over  and  over  again,  with  the  complex  eye 
complete  ;  if  the  front  of  the  eye  of  a  newt  be  cut  off,  a 
new  lens  is  regenerated ;  a  lizard  can  re-grow  the  tail 
which  it  has  surrendered  to  its  enemy ;  and  a  stork  can 
re-grow  a  considerable  portion  of  its  lower  jaw. 

There  is  in  certain  types  a  remarkable  exuberance  of 
regenerative  power.  This  is  notably  true  of  Amphibians. 
If  the  fore-limb  of  a  newt  or  salamander  is  cut  off  across 
the  humerus,  it  is  normally  re-grown,  and  this  happens 
whether  it  is  an  adult  or  a  larva.  Nay  more,  in  the  same 


554 


THE    WONDER  OF  LIFE  555 

animals,  the  removal  of  the  entire  limb  and  shoulder  girdle 
of  one  side  may  still  be  followed  by  the  re-growth  of  both 
— which  is  an  extraordinary  instance  of  regenerative 
capacity. 

In  Linckia  guildingii,  a  starfish  common  on  the  reefs  of 
Jamaica,  the  regenerative  capacity  is  not  less  exuberant. 
Dr.  Hubert  Lyman  Clark  observed  that  arms  or  rays 
severed  at  some  distance  from  the  central  disc  give  rise 
to  new  discs  and  rays,  just  as  well  as  those  which  separate 
close  to  the  disc.  Rays  are  thrown  off  at  irregular  inter- 
vals for  a  long  period,  if  not  throughout  life.  In  those 
rays  growth  continues,  especially  at  the  broken  end,  where 
new  rays  soon  begin  to  appear,  radiating  out  from  a  new 
mouth.  It  seems,  indeed,  that  in  this  case  the  giving  off 
of  the  rays  and  their  subsequent  regeneration  of  an  entire 
starfish  must  be  regarded  as  an  important  mode  of 
asexual  multiplication. 

Analogous  Phenomena. — It  is  always  a  step  towards 
understanding  to  bring  one  kind  of  phenomenon  into  line 
with  others.  Thus  it  may  be  recalled  that  many  of  the 
results  of  experimental  embryology  show  that  part  of  an 
embryo  has  often  the  power  of  doing  much  more  in  the 
way  of  development  than  is  normally  required  of  it.  If 
one  of  the  first  two  cells  into  which  the  egg  of  a  sea-urchin 
or  a  lancelet  divides  be  separated  off,  it  may  form  a  com- 
plete embryo.  A  minute  nucleated  fragment  of  an  egg 
may  develop  into  an  embryo,  which  lives  for  a  short  time 
at  least. 

Secondly,  we  may  recall  the  familiar  fact  that  in  many 
animals  there  is  an  almost  continual  process  of  tissue- 
regeneration  going  on.  Worn-out  epidermic  cells,  glandular 
cells,  blood-corpuscles,  and  so  forth  are  all  replaced  by 


556  THE  WONDER  OF  LIFE 

what  we  may  call  a  process  of  continuous  growth.  To 
meet  the  exigencies  of  normal  life,  the  daily  wear  and  tear, 
there  is  a  continuation  of  local  growth,  which  has  certainly 
its  bearing  on  the  regeneration  of  accidentally  lost  parts. 
One  of  the  noteworthy  limitations  of  this  tissue-regenera- 
tion concerns  the  nervous  system  in  higher  animals,  for 
the  number  of  nerve- cells  does  not  appear  to  admit  of  any 
increase  after  birth. 

Thirdly,  it  seems  useful  to  remember  that  the  process 
of  asexual  reproduction  which  many  organisms  exhibit 
is  a  utilization  of  the  capacity  of  re-growing  the  whole 
from  a  part.  Among  Stinging  Animals,  Annelids,  Polyzoa, 
and  Tunicates  there  is  often  a  normal  giving  off  of  a  portion 
of  the  parent,  which  develops  into  a  new  individual.  It 
may  be  a  bud  or  an  area  of  the  body  or  a  fragment — it  is 
a  part  which  is  capable  of  re-growing  the  whole.  The  pro- 
cess is  certainly  to  be  brought  into  line  with  the  regenera- 
tion of  a  lost  part  and  with  the  regeneration  of  an  entire 
individual  from  an  artificially  excised  part. 

It  is  instructive  to  consider  cases  where  the  power  of 
asexual  reproduction,  which  is  normally  a  mere  alternative, 
may  become  the  main  or  exclusive  means  of  continuing  the 
species.  This  is  well  illustrated  by  the  case  of  an  Alpine 
Planarian,  studied  by  Voigt.  It  is  a  relict  of  glacial  con- 
ditions, a  northern  form,  abounding  in  the  hill  streams 
around  Bonn.  Observation  and  experiment  show  that 
warmth  hinders  its  sexual  reproduction  ;  out  of  4,000  speci- 
mens not  one  was  sexual;  it  is  keeping  its  foothold  in 
existence  solely  in  virtue  of  its  power  of  multiplying  by 
division.  In  other  words,  a  power  which  is,  to  begin  with, 
only  a  subsidiary  alternative,  may  in  special  circumstances 
become  of  essential  importance.  This  should  be  borne 


THE  WONDER  OF  LIFE  557 

in  mind  in  connection  with  the  re-growth  of  lost  parts. 

Fourthly,  it  may  be  profitable  to  keep  by  themselves 
those  cases  where  an  artificially  excised  small  fragment 
is  able  in  favourable  conditions  to  re-grow  an  entire  organ- 
ism. A  fragment  of  a  liverwort  thallus  will  re-grow  the 
whole  plant,  a  piece  of  Begonia  leaf  will  develop  into  a 
complete  plant  with  root  and  stem  and  flower,  a  corner  of 
potato-tuber  with  an  "  eye  "  has  the  same  capacity — so 
familiar  that  it  has  ceased  to  excite  our  wonder.  A  piece  of 
Sponge  may  be  cut  off  and  '  bedded  out '  ;  a  Hydra  may 
be  cut  into  many  parts  each  viable  ;  one  Planarian  worm, 
half  an  inch  long,  may  give  rise  to  a  dozen  worms  if  cut 
into  a  dozen  pieces. 

Julian  S.  Huxley  has  confirmed  H.  V.  Wilson's  observa- 
tions on  the  remarkable  behaviour  of  cells  strained  off 
from  chopped-up  sponge.  He  worked  with  a  common 
vase-like  calcareous  sponge,  Sycon  raphanus,  and  found 
that  some  of  the  cells  moved  like  amoebae  and  united  into 
small  confused  clumps  of  irregular  size — a  process  quite 
unlike  anything  that  occurs  in  the  ordinary  life  of  sponges. 
Then  followed  processes  of  re-organization  and  re-develop- 
ment, in  some  respects  like  those  of  normal  embryonic 
development.  Two  layers  of  cells  were  established, 
spicules  were  formed,  a  gastral  cavity  and  an  exhalent 
aperture  appeared,  and  one  of  the  '  regenerates '  lived 
and  grew  as  a  functioning  sponge  for  several  weeks.  This 
illustrates  what  we  venture  to  call  the  indomitable  virility 
of  life. 

We  see,  then,  in  approaching  the  problem  of  the  regenera- 
tion of  lost  parts — say,  lizard's  tails,  newt's  legs,  snails' 
horns,  starfishes'  arms — that  it  is  useful  to  bear  in  mind 
some  cognate  phenomena  : — (1)  some  of  the  facts  of 


558  THE  WONDER  OF  LIFE 

experimental  embryology  which  show  that  a  cleavage-cell 
or  blastomere  may  have  no  small  amount  of  residual  power 
beyond  that  which  it  normally  expresses  ;  (2)  the  normal 
process  of  tissue-regeneration  which  makes  good  the  every- 
day wear  and  tear  ;  (3)  the  frequency  of  asexual  reproduc- 
tion by  buds  or  by  fission ;  and  (4)  those  cases  where  a 
minute  fragment  re-grows  the  whole. 

Unequal  Distribution  of  Regenerative  Capacity. — 
One  of  the  significant  facts  regarding  the  power  of  re-grow- 
ing lost  parts  is  its  unequal  distribution  among  the  various 
types  of  animals.  It  is  very  common  among  worm-types, 
but  almost  absent  in  Nematodes — perhaps  because  a  rupture 
of  the  body  in  these  worms  is  rapidly  fatal.  It  is  common 
among  Chsetopods,  but  there  is  not  much  of  it  in  leeches — 
partly  because  the  slippery  surface  and  tough  body- 
wall  make  these  animals  but  little  liable  to  injury.  It  is 
very  general  among  Arthropods,  where  legs  are  so  liable 
to  breakage,  but  there  is  not  much  of  it  among  Molluscs, 
perhaps  because  most  of  these  are  shut  up  in  shells.  It  is 
well  seen  in  Amphibians,  especially  among  tadpoles  and 
newts,  but  it  is  not  much  in  evidence  among  fishes.  It  is 
common  among  lizards,  but  there  is  little  of  it  among 
snakes.  A  bird's  toe  or  the  end  of  a  mammal's  tail  can 
hardly  be  regarded  as  more  complex  than  a  starfish's  arm 
or  the  visceral  organs  inside  a  feather-star's  calyx,  but  while 
regeneration  is  exceedingly  characteristic  of  Echinoderms, 
it  is  at  a  minimum  in  Birds  and  Mammals. 

When  we  follow  the  inequality  of  distribution  into  greater 
detail  it  becomes  at  once  more  striking  and  more  luminous. 
It  begins  to  reveal  its  significance.  In  many  families  of 
lizards  it  is  the  rule  that  a  lost  tail  is  regenerated,  but  in 
those  lizards  which  strike  with  their  tails,  Werner  has 


THE  WONDER  OF  LIFE  559 

shown  that  the  regeneration  is  absent  or  very  incomplete. 
Has  the  absence  of  it  something  to  do  with  the  fact  that 
in  those  aggressive  lizards  that  use  their  tail  as  a  weapon, 
the  loss  of  the  tail  is  not  likely  to  occur  ?  Perhaps  a  clearer 
case  is  that  of  the  Chameleon,  which  coils  its  prehensile 
monkeyish  tail  round  the  branch.  There  seems  to  be  little 
or  no  regeneration,  if  the  tail  be  cut  off.  Has  the  absence 
of  it  something  to  do  with  the  fact  that  in  the  case  of  the 
quaint  Chameleon,  the  loss  of  the  tail  is  not  likely  to  occur  ? 
Some  of  the  limitations  are  less  readily  interpreted.  Thus 
the  weakly  developed  limbs  of  Siren  and  Proteus  are  not 
regenerated,  but  the  well-developed  limbs  of  the  newt  are. 
A  salamander  will  re-grow  an  amputated  limb  if  the  bone 
be  cut  across  and  not  disarticulated,  but  in  a  frog  the  wound 
heals  without  regenerating.  The  puzzle  is  why  there  should 
be  such  differences  in  the  regenerative  capacity  of  nearly 
related  types.  Another  instructive  case  is  that  of  the  sea- 
urchin  which  cannot  regenerate  anything  but  its  spines. 
Why  is  there  this  limitation  in  a  member  of  the  Echinoderm 
class  in  which  the  regenerative  capacity  is  widespread  and 
highly  developed  ?  Is  it  that  the  globular  sea-urchin  is 
not  subject  to  the  same  risks  as  a  starfish  or  a  brittle-star  ? 
Another  general  fact,  which  points  the  way  to  a  theo- 
retical interpretation,  is  that  regeneration  of  internal  parts 
is  very  rare  among  backboned  animals,  and  rare  even  among 
backboneless  animals  except  in  cases  like  those  of  earth- 
worms and  starfishes,  where  the  loss  of  part  of  the  body 
necessarily  injures  the  internal  organs,  such  as  the  alimen- 
tary and  nervous  systems.  If  a  rabbit's  spleen  be  removed, 
it  is  not  replaced ;  if  a  fragment  be  left,  it  does  not  grow 
larger.  The  removal  of  a  kidney,  a  thyroid,  a  liver-lobe, 
and  so  on,  is  not  known  to  be  followed  by  regenerative 


56o 


THE  WONDER  OF  LIFE 


growth.     Only  in  the  case  of  reproductive  organs  does  a 
remnant  grow  to  replace  what  has  been  removed. 

Lessona's  Law.  —  These  two  sets  of  facts  —  the  rarity  of 
regeneration  in  the  internal  organs  of  higher  animals,  and 
the  strangely  unequal  distribu- 
tion of  the  capacity  —  point  to 
a   conclusion  which   seems   to 
have  occurred  to  several  natu- 
ralists    from      R6aumur      to 
Weismann,    and    was    clearly 
summed  up   in   1868   by  the 
Italian      naturalist      Lessona. 
According  to  '  Lessona's  law  ', 
regeneration  tends  to  be  well 
marked  in  those  animals,  and 
in  those  parts  of  animals  which 
are    in    the    course    of    their 
natural  life  particularly  liable 
to    injury.      To    which,    two 
saving  clauses  must  be  added, 
that  the  lost  part  be  of  some 
-Comet  form  of  starfish  ^  importance,  and  that  the 
(Linckia).    (After  Richters.)  wound   or   injury   be    not    in 
An  arm   and  a  portion   of.       lfvi    i     ,      •>       r  j.   i       mi  • 
disc  regenerating  the  other   itself  likely  to  be  fatal.      This 
four  arms.   M,  the  mouth  ;  theory,  which   is   really   Dar- 
BA,  a  regenerating  arm  ;  OA, 
the  original  arm  ;  AG,  the  wiman,    has     been     re-stated 


by  Weismann  in  the  words: 
'  the    power    of    regeneration 

possessed  by  an  animal  or  by  a  part  of  an  animal  is  regu- 
lated by  adaptation  to  the  frequency  of  loss,  and  to  the 
extent  of  the  damage  caused  by  the  loss  '. 

It  is  evident,  at  once,  that  the  lank  and  slender  bodies 


THE  WONDER  OF  LIFE  561 

of  worms,  the  long  arms  of  starfishes  and  brittle-stars,  the 
sprawling  limbs  of  newts,  the  long  tails  of  lizards,  and 
so  on,  are  naturally  liable  to  injury,  and  that  a  re- 
generative capacity  is  one  which  natural  selection  would 
foster. 

It  is  also  evident  that  internal  organs  are  much  less  likely 
to  be  cut  out  than  external  organs  are  to  be  cut  off.  It  is 
also  certain  that  visceral  wounds  are  much  more  likely  to 
be  fatal  in  Vertebrates  than  in  Invertebrates,  so  that  a 
regenerative  capacity  in  the  former  would  be,  so  to  speak, 
a  quality  wasted,  whereas  in  the  less  sensitive  Invertebrates, 
where  it  often  occurs,  it  is  very  much  in  demand.  If  the 
retention  and  specialization  of  the  regenerative  capacity 
has  been  evolved  as  an  adaptive  character,  it  must  obvi- 
ously be  restricted  to  cases  where  the  injury  is  of  a  kind  not 
likely  to  be  fatal. 

It  will  be  observed  that  Lessona's  law  does  not  touch  the 
question  of  the  origin  of  the  regenerative  capacity,  nor  the 
question  of  how  the  capacity  resides  in  the  lizard's  tail  or 
in  the  snail's  horn,  nor  the  process  of  re-growing  a  complex 
structure  from  a  stump.  It  is  a  theory  of  the  distribution 
of  the  regenerative  capacity — why  is  it  here  and  not  there, 
why  is  it  strong  in  some  animals  and  weak  in  others,  why 
it  is  well  marked  in  regard  to  some  parts  and  not  at  all 
marked  in  regard  to  others.  The  question  is  whether  it  is 
a  sufficient  formula  to  cover  the  known  facts  in  regard  to 
the  distribution  of  the  regenerative  capacity. 

Testing  the  Theory. — One  way  of  testing  the  theory 
is  to  inquire  whether  there  are  any  or  many  well-authenti- 
cated cases  of  the  regeneration  of  parts  which  would  not 
be  likely  to  be  injured  or  lost  in  the  natural  conditions  of 
the  animal's  life.  A  number  of  difficult  cases  have  been 

o  o 


562  THE  WONDER  OF  LIFE 

brought  forward,  and  we  may  consider  a  few  which  may 
be  called  typical. 

There  is  the  well-known  case  of  the  stork's  bill,  which 
Weismann  admitted  to  be  difficult.  The  upper  half  was 
accidentally  broken  off,  the  lower  jaw  was  amputated  to  the 
same  length,  in  the  course  of  time  both  were  regenerated — 
a  very  remarkable  achievement. 

Now  is  there  any  evidence  that  such  a  serious  injury 
might  occur  in  ordinary  life  ?  If  it  is  not  a  loss  that  is  at  all 
likely  to  occur,  then  it  is  not  easy  to  understand  why  any 
organic  provision  should  be  made  for  its  compensation. 
The  difficulty  was  lessened  by  the  report  of  Bordage,  that 
in  cock-fights  similar  injuries  were  frequent  and  were  often 
followed  by  very  remarkable  regeneration.  In  one  case 
the  premaxillae  and  part  of  the  mandible  were  torn  off — a 
large  fraction  of  the  entire  beak — yet  both  bones  and  horny 
coverings  were  regenerated.  Now  cock-fighting,  though 
elaborated  by  men  of  more  or  less  evil  device,  is  a  natural 
phenomenon.  Cocks  are  given  to  fighting  furiously,  inj  uries 
are  frequent,  and  it  is  just  the  sort  of  ever-recurrent  injury 
for  the  reparation  of  which  provision  might  be  made. 
When  we  discover,  furthermore,  that  male  storks  also  fight 
furiously,  sometimes  fatally,  the  difficulty  of  the  stork's 
bill  seems,  as  Weismann  says,  to  become  an  exception 
proving  the  rule. 

Another  difficult  case  which  Weismann  discusses  is  that 
the  eye  of  the  newt  (Triton)  may  be  regenerated,  as  Bonnet 
and  Blumenbach  showed  long  ago,  after  serious  injury. 
We  now  know  that  if  the  lens  alone  be  carefully  taken 
out,  it  will  be  replaced.  These  are  very  remarkable 
instances  of  regeneration,  but  the  question  immediately 
arises,  What  chance  is  there  that  in  natural  conditions  a 


THE  WONDER  OF  LIFE  563 

newt  should  have  its  eye  gouged  out  ?  To  this  Weismann 
answers  that  newts  fight  furiously,  at  any  rate  at  the 
breeding  season,  and  often  injure  one  another ;  and  that 
the  larvae  of  the  large  water-beetle  (Dytiscus  marginalia) 
often  attack  newts  just  behind  the  head.  Moreover  the 
water-snail  Limnsea,  though  usually  vegetarian,  is  some- 
times found  killing  a  newt,  getting  upon  its  back  and 
filing  the  skin  with  its  radula.  It  is  probable  that 
a  more  complete  knowledge  of  the  life  of  Amphibians 
would  show  that  serious  injury  to  the  eye  is  not  a  rare 
casualty. 

A  very  interesting  case  is  given  by  Bordage.  In  locusts 
and  related  insects,  the  loss  of  one  of  the  first  two  pairs  of 
legs  is  followed  by  regeneration.  On  the  other  hand,  the 
posterior  or  third  pair  of  legs,  which  are  of  great  importance 
in  jumping,  are  not  regenerated.  Now  why  should  this 
be,  that  the  less  important  may  be  re-grown,  while  the  more 
important  are  not  ?  This  seems  quite  inconsistent  with 
Lessona's  law.  But  Bordage  points  out  that  the  loss  of 
the  posterior  legs  almost  prevents  moulting,  leaves  the 
locusts  exposed  to  great  danger,  and,  furthermore,  prevents 
breeding.  Perhaps  therefore  the  case  is  covered  by  the 
corollary  to  Lessona's  law — '  provided  the  injury  be  not 
fatal '.  Nor  can  one  conceive  how  organic  provision 
could  be  made  for  an  injury  which  prevents  breeding.  The 
prevention  of  breeding  is  a  full-stop  to  the  evolution  of  an 
adaptive  feature  of  any  kind. 

Some  of  the  cases  of  regeneration  are  very  remarkable. 
Kammerer  has  found  that  in  the  common  house-fly  (Musca 
domestica)  and  in  the  blow-fly  (Calliphora  vomitoria) 
amputation  of  a  wing  is  not  followed  by  any  result,  yet 
tearing  off  a  wing  from  a  newly  pupated  fly  is  sometimes 


564  THE  WONDER  OF  LIFE 

followed  by  re-growth.  The  new  wing  is  at  first  homogene- 
ous and  transparent,  it  subsequently  gets  veins  which 
seem  to  be  after  the  normal  pattern.  The  regeneration  of 
a  wing  has  also  been  observed  in  the  meal-beetle  (Tenebrio). 
In  Nature  an  insect  bereft  of  wing  would  be  likely  to  die, 
nor  is  the  accident  very  likely  to  happen  often  unless  in 
Lepidoptera,  where  the  removal  of  a  wing  is  followed  by  no 
result.  It  seems  difficult  therefore  to  suppose  that  the 
regenerative  capacity  is  always  adaptive. 

An  interesting  peculiarity  in  connection  with  regenera- 
tion in  the  starfish  may  also  be  used  as  a  test  case.  Miss 
Helen  D.  King  points  out  that  in  Aster ias  vulgaris  it  is 
quite  usual  for  an  isolated  arm  to  regenerate  the  whole  if 
it  has  a  fraction  of  the  central  disc  left.  '  Comet-forms ' 
are  not  infrequent,  which  consist  of  a  fully- developed  arm, 
a  partially  formed  disc,  and  four  beginnings  of  the  arms 
which  are  missing.  One  of  these  forms  is  figured  (Fig.  91), 
and  every  shore-naturalist  is  familiar  with  every  possible 
transition  between  the  single  arm  and  the  intact  starfish. 
All  this  is  well  known,  but  what  Miss  King's  experiments 
brought  out  was  the  fact  that  while  the  ventral  part  of 
an  arm  may  regenerate  the  dorsal  surface,  the  converse 
does  not  occur.  It  may  be  said,  of  course,  that  this  is 
simply  because  of  the  complexity  of  the  ventral  surface, 
with  its  tube-feet,  water-vessel,  nerve-strand,  and  so  on. 
But  it  is  just  possible  that  the  reason  may  be  different,  and 
connected  with  the  obvious  fact  that  the  dorsal  surface  is, 
in  natural  conditions,  much  more  open  to  attack  and  injury 
than  the  ventral  surface  which  adheres  to  the  rock.  Again, 
perhaps,  the  exception  proves  the  rule. 

Another  apparent  difficulty  which  turns  out  to  be  a 
corroboration  is  expounded  by  Bordage.  The  lower  or 


THE  WONDER  OF  LIFE  565 

tarsal  joints  of  the  legs  of  locusts  and  the  like  are  readily 
dislocated,  and  in  the  two  front  pairs  they  are  readily 
regenerated.  It  requires  great  force  to  break  the  leg  near 
the  top  between  joints  1  and  2  (coxa  and  trochanter), 
or  still  more  between  parts  2  and  3  (trochanter  and 
femur).  The  injury  is  often  fatal.  But  the  remark- 
able point  is  that  if  the  insect  survives  and  is  young, 
regeneration  may  be  effected,  especially  if  the  dislocation 
is  between  joints  2  and  3,  ivhere  it  is  most  difficult.  This 
seems  to  be  an  extremely  difficult  case,  for  after  making 
all  allowances  for  the  various  and  violent  ways  in  which 
locusts  may  be  pulled  about  by  one  another,  or  by  birds 
and  other  enemies,  it  is  difficult  to  see  how  in  natural  con- 
ditions sufficient  force  would  be  exerted  to  break  the 
leg,  and  still  more  difficult  to  understand  why  regenera- 
tion should  most  frequently  follow  when  the  breakage 
occurs  at  the  most  difficult  place. 

Yet  the  difficulty  is  not  insurmountable,  for  observation 
of  the  frequent  moultings  shows  that  when  the  locust  is 
struggling  out  of  its  old  clothes  or  cuticle,  breakage  at 
the  joints  is  very  apt  to  occur,  particularly  at  the  trochanter- 
femur  articulation,  which  afterwards  becomes  so  strong. 
The  difficulty  disappears  and  becomes  an  argument  in 
favour  of  the  view  that  the  distribution  of  the  regenerative 
capacity  is  adaptive. 

Similarly,  Bordage  has  shown  in  regard  to  Walking- 
Stick  Insects,  or  Phasmids,  where  the  assaults  of  birds  and 
lizards  seemed  to  afford  insufficient  reason  for  the  pre- 
valent habit  of  breaking  off  a  leg  at  a  particular  line  and 
re-growing  it  thence,  that  the  breakages  during  emergence 
from  the  egg  or  from  the  cast  moults  have  probably  fur- 
nished sufficient  reason  for  the  evolution  of  the  restorative 


566  THE  WONDER  OF  LIFE 

provision.  On  a  point  like  this  it  is  interesting  to  get 
precise  facts,  and  Bordage  notes  that  out  of  a  hundred 
Phasmids,  nine  died  during  moulting,  twenty-two  tore 
themselves  free  with  the  loss  of  one  or  more  legs,  and  only 
sixty- two  survived  without  any  loss.  In  short,  breakage 
during  moulting  is  a  frequently  recurrent  casualty,  pro- 
vision for  which  would  certainly  be  favoured  by  natural 
selection. 

Another  difficulty  is  presented  by  the  regeneration  of  the 
abdominal  limbs  of  hermit-crabs,  which  are  normally  pro- 
tected by  the  Gastropod  shell  which  the  Crustacean  borrows. 
There  are  five  of  these — the  first  very  rudimentary  in  the 
males,  but  used  for  carrying  the  eggs  in  the  females ;  the 
fourth  and  fifth  used  to  fix  the  hermit-crab  to  the  central 
pillar  of  the  borrowed  shell.  It  is  evident  that  there  is 
little  likelihood  of  these  limbs  being  nipped  off — extremely 
little  in  the  case  of  the  two  hindmost  pairs.  But  Professor 
T.  H.  Morgan  has  shown  that  all  the  limbs  of  hermit-crabs 
are  capable  of  regeneration,  though  they  do  not  all  grow 
again  equally  often,  the  anterior  abdominal  appendages 
being  less  frequently  renewed  than  the  more  exposed 
thoracic  limbs,  for  even  these  are  not  always  restored  after 
loss.  He  therefore  argues  that  there  is  here  no  relation 
between  frequency  of  loss  and  regenerative  capacity — a 
thesis  quite  counter  to  the  idea  of  Lessona's  law.  Weis- 
mann's  general  answer  is  that  the  regenerative  capacity 
shown  by  the  hermit-crab's  abdominal  limbs  may  be  a 
persistent  inheritance  from  ancestral  forms  which  must 
have  had  exposed  tails.  Moreover,  one  would  like  to 
inquire  particularly  into  the  life  of  hermit-crabs  to  find 
out  whether  there  are  not  now — in  the  combats,  in  the 
flitting  from  one  house  to  another,  and  particularly  in  the 


THE  WONDER  OF  LIFE  567 

moultings — some  very  good  present  reasons  for  the  retention 
of  the  regenerative  capacity  in  the  abdominal  appendages. 

Imperfect  Regenerations. — Another  objection  to  the 
theory  which  interprets  the  distribution  or  occurrence  of 
the  regenerative  capacity  as  adaptive  is  found  in  those 
strange  and  highly  interesting  cases  where  the  re-growth 
takes  place,  but  not  according  to  pattern.  As  Spallanzani 
showed  in  1768  and  T.  H.  Morgan  in  1899,  a  decapitated 
earthworm  may  grow  a  second  tail  (as  shown  by  the  dis- 
position of  the  excretory  tubules  or  nephridia)  instead  of 
replacing  its  lost  head.  But  this  only  serves  to  show  that 
the  regenerative  process  is  liable  to  go  wrong  at  times  just 
as  the  embryonic  development  does.  The  fact  that  a 
headless  creature  is  sometimes  born  does  not  affect  the 
general  conclusion  that  development  is  a  regulated  and 
harmonious  process. 

Werner  points  out  that  when  a  lizard  re-grows  its  tail,  it 
does  not  always  adhere  to  the  pattern.  When  the  scales 
are  comparatively  simple,  the  regeneration  is  almost  perfect, 
but  when  the  scales  are  complex  and  there  is  much  orna- 
mentation, the  regenerated  tail  is  simpler  than  the  one 
that  was  lost ;  it  tends  to  be  an  ancestor's  type  of  tail.  Hence 
the  wit  has  suggested  that  to  find  out  a  lizard's  pedigree, 
you  have  only  to  pull  off  its  tail.  Perhaps  a  truer  way  of 
stating  the  case,  however,  is  that  the  regenerated  tail  is 
nearer  the  embryonic  type,  which  is  not  surprising  if 
regeneration  be  due  to  a  local  persistence  and  re-awakening 
of  embryonic  growing  powers. 

There  seems  to  be  a  widespread  tendency  towards  the 
reproduction  of  a  simpler  or  ancestral  form,  or,  in  some  cases, 
of  a  simpler  and  more  embryonic  form.  Thus  in  cock- 
roaches and  walking-stick  insects  (Phasmids),  which  have 


568  THE  WONDER  OF  LIFE 

normally  five  tarsal  joints  at  the  end  of  the  leg,  the  regener- 
ated limb  has  only  four  tarsal  joints,  which  is  believed  to 
be  the  ancestral  number.  Weismann  cites  the  observation 
of  Fritz  Miiller,  that  in  a  Brazilian  shrimp,  Atyoida  poti- 
morim,  the  long  clawed  forceps  are  replaced  in  regeneration 
by  the  older  short-fingered  type  of  forceps,  seen  in  the 
allied  genus  Caridina.  In  both  these  cases  it  might  be 
said  that  the  regeneration  was  economical  and  that  not 
more  than  a  workable  substitute  for  the  lost  part  was 
re-grown.  But  this  cannot  be  the  explanation,  for  we  know 
that  regeneration  will  take  place  perfectly  in  half-starved 
animals.  Furthermore,  there  are  cases  where  the  regener- 
ated part,  though  more  ancestral,  is  not  more  economical 
of  material.  Thus  Barfurth  calls  attention  to  the  very 
suggestive  fact  that  the  four-fingered  hand  of  the  Axolotl 
is  replaced  after  amputation  by  a  more  typical  five-fingered 
hand. 

Weismann  has  suggested  a  speculative  theory  of  these 
cases.  He  supposes  that  there  are  regeneration-germs 
which  come  to  reside  in  areas  particularly  liable  to  injury 
(like  the  cambium- cells  in  various  parts  of  plants),  and  he 
further  supposes  that  these  have,  in  their  developmental 
power,  lagged  a  little  behind  the  level  of  the  part  to  which 
they  correspond.  They  are  able  to  replace  it,  but  not  quite 
up  to  the  contemporary  grade  of  evolution.  It  must  be 
remembered  that  the  regeneration  tends  to  be  rapid  com- 
pared with  the  original  development,  and  that  the  con- 
ditions are  different.  Perhaps  some  stimulus  is  awanting 
to  incite  the  regeneration  to  go  a  step  further. 

It  must  be  admitted  that  in  many  cases  the  substitute 
that  replaces  the  lost  part  is  not  quite  correct,  not  quite 
up  to  the  mark.  In  place  of  a  lost  leg  an  insect  may  grow 


THE  WONDER  OF  LIFE  569 

an  antenna  ;  in  place  of  an  antenna  a  leg.  Instead  of  a 
lost  abdominal  limb  the  edible  crab  may  grow  a  walking 
leg,  which  is  very  much  out  of  place,  and  instead  of  a  lost 
stalked-eye  the  lobster  may  grow  an  antenna.  Many  cases, 
indeed,  are  known  where  a  Crustacean  does  not  get  an  eye 
for  an  eye,  but  something  simpler.  Most  of  these  cases 
of  imperfect  regeneration  concern  animals  whose  limbs 
normally  pass  from  one  form  to  another  with  successive 
moultings,  and,  as  Przibram  suggests,  it  is  worth  asking 
whether  the  antenna  instead  of  an  eye  was  really  the  final 
result  of  the  regenerative  process.  The  animals  should  be 
kept  alive  when  possible,  and  the  observation  continued 
until  after  the  next  moult.  In  his  experiments  on  the 
common  water-flea,  Daphnia,  and  on  the  Isopod,  Asellus, 
he  found  that  the  regenerated  limb  was  not  at  first  perfect, 
but  became  normal  after  repeated  moultings. 

Regeneration  and  Embryonic  Development. — In 
many  cases  the  process  by  which  regeneration  is  effected 
is  very  like  the  normal  process  of  typical  development, 
which  is  perhaps  what  one  should  expect  on  a  priori  grounds. 
The  ectoderm  or  outer  layer  of  the  cut  surface  furnishes 
the  ectoderm  of  the  re-growth,  and  the  mesoderm  the 
mesoderm.  But  in  some  cases  the  regenerative  growth 
is  very  different  from  that  which  occurs  in  embryonic 
development,  and  we  have  to  face  the  puzzle  that  the  same 
result  may  be  reached  by  two  different  paths. 

When  the  anterior  end  of  a  Naiad — a  freshwater  worm — 
is  cut  off,  an  ectodermic  cap  is  formed,  according  to  Hepke, 
over  the  wound ;  in  the  concave  interior  of  this  cap  there 
gradually  appear  all  the  organs  to  be  replaced ;  muscles, 
which  are  normally  mesodermic,  are  formed  by  cells  mig- 
rating from  the  ectoderm,  and  a  piece  of  food- canal,  which 


570  THE  WONDER  OF  LIFE 

ought  by  rights  to  be  endodermic,  is  formed  by  the  ectoderm. 
There  are  not  a  few  cases  of  this  sort,  and  it  is  plain  that 
regenerative  growth  does  not  necessarily  follow  the  path 
of  embryonic  development.  The  same  sort  of  difficulty 
arises  in  connection  with  the  buds  of  Tunicates  and 
Polyzoa  which  reach  the  same  general  result  as  a  fertilized 
ovum,  but  by  quite  different  paths.  Perhaps  we  have 
here  a  hint  that  we  may  create  unnecessary  difficulties  by 
making  too  much  of  the  distinctiveness  of  the  germinal 
layers. 

Another  much- discussed  case  must  be  cited.  Calucci, 
Wolff,  and  Miiller  have  made  the  experiment  of  extracting 
the  lens  of  Triton,  with  the  result  that  it  was  normally 
regenerated.  From  what,  however  ?  Not  from  remnants 
of  the  lens,  for  there  were  none,  but  from  the  iris,  with 
which  the  lens  (a  product  of  the  ectoderm  in  front  of  the 
optic  cup)  has  no  genetic  connection.  That  an  iris  should 
be  able  to  regenerate  an  iris  would  be  consonant  with  the 
general  facts  of  regeneration,  but  it  seems  to  be  able  to 
re-make  a  lens,  in  whose  original  making  it  plays  no  part. 
It  may  be  pointed  out  that  the  posterior  epithelium  of  the 
iris  is  ectodermic  like  the  lens,  and  furthermore  that  the 
newt  is  an  animal  with  great  regenerative  power  in  many 
parts,  and  may  be  contrasted  with  an  animal  like  the  rabbit, 
where  regeneration  of  the  lens  does  not  occur  unless  some 
portion  of  the  lens  be  left.  Perhaps,  however,  the  case  of 
the  newt's  lens  points  to  the  conclusion  that  the  residual 
germinal  capacity,  localized  here  and  there  in  animals,  is 
more  general  and  less  specific  than  is  sometimes  supposed, 
and  that  what  occurs  in  any  particular  instance  is  under 
some  sort  of  regulation,  so  that  what  is  most  needed  tends 
to  be  done. 


THE  WONDER  OF  LIFE  571 

The  Wonder  of  Regeneration. — It  is  striking  to  see 
how  from  within  its  cuticular  sheath  there  suddenly  bursts 
forth  a  beautifully  formed  lobster-limb,  replacing  one  that 
has  been  lost.  It  is  liberated  at  a  moult,  and  stretches 
itself  out  like  a  Jack-in-the-Box.  The  occurrence  seems 
almost  magical,  but  we  must  not  be  misled.  The  abrupt- 
ness of  the  phenomenon  is  wholly  superficial,  there  has  been 
a  long  period  of  gradual  differentiation  within  the  husk 
of  the  limb-bud.  There  are  not  many  Jack-in-the-Box 
phenomena  in  organic  Nature.  Her  magic  is  quiet. 

Therefore  one  of  the  things  to  be  borne  in  mind  is  that 
in  regenerative  growth,  just  as  in  embryonic  development, 
one  phase  naturally  and  gradually  leads  on  to  the  next.  The 
stump  of  a  snail's  horn  will  re-grow  the  whole  horn,  with 
the  eye  at  the  tip  included,  and  will  re-grow  it  not  once  but 
many  times.  But  there  is  nothing  sudden,  the  horn  is 
fashioned  with  a  gradually  increasing  perfection,  reminding 
one  of  the  growth  of,  let  us  say,  a  coronet  in  the  craftsman's 
hands.  The  words  gradual  differentiation  and  integration 
do  not  solve  any  mystery,  but  they  may  save  us  from  a 
false  impression. 

We  are  probably  unable  in  the  present  state  of  science 
to  utilize  to  proper  advantage  the  analogies  between  cry- 
stallization and  growth  ;  but  it  is  interesting  to  remember 
that  a  minute  fragment  of  alum  fashioned  artificially 
into  a  sphere,  or  a  cylinder,  or  a  lens,  will,  when  dropped 
into  a  solution  of  alum,  develop  into  a  perfect  octahedron, 
through  what  Rauber  has  called  an  imperfect  embryonic 
stage.  A  sphere  of  saltpetre  will  similarly  regenerate  a 
rhombic  prism,  and  any  mutilation  of  a  crystal  will  be 
followed  by  a  restoration  of  the  normal  form.  Now  the 
gap  between  the  little  spherule  of  alum  and  the  perfect 


572  THE  WONDER  OF  LIFE 

octahedron  is  remotely  comparable  to  the  gap  between  the 
regenerative  hood  that  forms  at  the  anterior  end  of  a 
decapitated  freshwater  worm  and  the  perfectly  re-grown 
head.  In  both  cases  there  is  a  gradual  series  of  differentia- 
tions and  integrations  connecting  the  beginning  and  the 
end. 

Again,  without  detracting  from  the  genuine  wonder  of 
the  facts  of  regeneration,  we  may  reasonably  seek  to  bring 
them  into  line  with  analogous  phenomena,  and  we  have 
already  referred  to  asexual  multiplication,  tissue  replace- 
ment, and  the  like.  Let  us  recall  also  what  occurs  inside 
the  pupa  case  of  a  fly,  where  the  larval  body  is  literally 
disintegrated,  and  certain  minute  groups  of  cells  (the 
imaginal  discs)  act  among  the  debris  as  the  centres  of  a 
reconstruction  on  an  entirely  new  plan. 

When  we  think  of  the  earthworm  growing  a  new  head, 
or  the  lizard  a  new  tail,  or  the  newt  a  new  lens — all,  as  it 
were,  at  command — we  must  try  to  allow  for  the  influence 
of  environing  stimuli.  The  residual  germinal  power  in  the 
animal  counts  for  much,  but  this  operates  under  the  influ- 
ence of  a  particular  environment,  which  also  counts  for 
much,  though  not  for  so  much.  Perhaps  this  point  may 
be  best  understood  by  reference  to  what  is  technically  called 
heteromorphosis,  which  means  that  in  certain  conditions 
the  re-growth  departs  from  its  ordinary  mode  of  procedure. 

If  an  inch  or  two  be  cut  from  the  cylindrical  stalk  of 
the  common  zoophyte  Tubularia,  and  one  end  be  stuck  in 
the  sand,  a  head  may  be  re-grown  at  the  free  end  whether 
that  was  originally  turned  towards  the  head  or  towards 
the  base.  But  if  both  ends  be  left  free,  the  piece  re- 
generates a  head  at  each  end.  Evidently  the  environ- 
mental influences  count  for  something  here.  There  are 


THE  WONDER  OF  LIFE  573 

many  similar  cases  which  suggest  that  the  result  is,  as  it 
were,  a  compromise  between  the  inherent  growth-tendencies 
of  the  organism  and  the  environmental  stimuli  operative  in 
each  case. 

Theoretical  Considerations. — In  what  way  is  it 
possible  for  us  to  imagine  the  regenerative  capacity  of 
organisms?  A  crocodile  loses  a  tooth,  but  beneath  its 
hollow  base  there  lay  another  which  now  fills  the  gap. 
Not  far  off  there  is  a  rudiment  of  another,  and  so  on.  The 
adder  casts  a  fang,  but  there  is  another  ready  to  slip  into 
its  place,  and  to  re-establish  in  a  very  interesting  way  the 
connection  with  the  poison  duct.  Not  far  off  there  is  a 
rudiment  of  another  fang,  and  so  on.  But  when  a  crab 
loses  a  claw  there  is  no  under-study  lying  ready  at  the  area 
of  rupture.  There  is  no  rudiment  of  a  visible  nature,  and 
yet  the  regeneration  is  duly  effected.  How  can  we  con- 
ceive of  this  ? 

In  certain  cases,  as  in  plants,  there  is  visible  evidence 
of  persisting  embryonic  tissue — the  cambium — which 
has  retained  the  formative  capacity  of  the  original  fertilized 
egg-cell.  In  many  of  the  lower  animals,  such  as  polyps, 
division  of  labour  has  not  gone  very  far,  and  there  are 
visible  '  interstitial  cells  '  which  have  remained  undifferen- 
tiated  and  might  be  compared  to  the  cambium  cells  of 
plants.  But  in  most  of  the  cases  which  we  have  discussed 
in  this  chapter  regeneration  takes  place  from  amid  a 
stump  of  differentiated  cells.  In  some  instances  there  is 
an  apparent  undoing  of  the  differentiation,  a  return  to  a 
simpler  type,  and  a  multiplication  at  a  embryonic  level. 
Sometimes  considerable  assistance  appears  to  be  afforded 
by  migrant  amoeboid  cells  of  the  body — the  phagocytes — 
which  appear  on  the  scene  of  the  accident  and  are  very 


574  THE  WONDER  OF  LIFE 

active  in  various  ways.  But  they  are  by  no  means  indis- 
pensable. On  the  whole,  in  the  present  state  of  our  know- 
ledge, it  seems  that  the  best  working  hypothesis  is  Weis- 
mann's.  He  supposes  that  the  germ-plasm  includes  special 
'  regeneration-determinants  '  which  are  distributed  appro- 
priately through  the  body  and  lie  quietly  like  garrisons  in 
strategic  places,  awaiting  a  possible  awakening  stimulus. 
Perhaps,  however,  it  is  at  present  wiser  to  leave  our 
conception  of  the  arrangements  for  regeneration  somewhat 
vague,  and  to  concentrate  attention  on  the  case  for  Les- 
sona's  law — that  regenerative  capacity  tends  to  occur  in 
those  animals  and  in  those  parts  of  animals  which  are  in 
the  natural  conditions  of  their  life  particularly  liable  to 
injury,  always  provided  that  the  part  lost  be  of  real  import- 
ance, and  that  the  injury  be  not  fatal.  All  of  which  comes 
to  this,  that  the  distribution  of  the  regenerative  capacity 
is  adaptive,  and  can  be  accounted  for  on  the  theory  of 
Natural  Selection. 


THE  CROWNING  WONDER  OF  EVOLUTION. 

We  have  become  so  familiar  with  the  general  idea  of 
organic  evolution  that  we  have  ceased  to  wonder  enough. 
It  should  be  a  thought  to  thrill  us,  that  we  and  the  multi- 
tudinous, varied,  intricate,  and  always  beautiful  world  of 
life  around  us  have  grown  by  infinitely  slow  gradations 
from  an  apparently  simple  beginning.  Through  unreckon- 
able  ages  Life  has  been  slowly  creeping  upwards,  possessing 
and  conquering  the  earth  ever  more  thoroughly,  unfolding 
new  and  unsuspected  potentialities  seon  after  aeon,  and 
affording  us  in  fact  no  small  part  of  the  material  that  has 
gone  to  build  up  our  conception  of  Progress. 


THE  WONDER  OF  LIFE  575 

It  is  a  grand  piece  of  history  beyond  doubt — the  pre- 
historic history  of  the  organic  world.  If  our  conception 
is  right  at  all,  there  once  was  a  time  when  the  living  creatures 
of  the  Earth  were  very  minute  corpuscles  of  living  matter 
— very  simple  but  individuated,  able  to  feed,  grow,  and 
multiply,  able  to  enregister  their  experiences.  We  must 
try  to  think  of  them  as  simpler  than  any  of  the  Protists 
that  are  visible  to-day.  Perhaps  the  ultra- microscopic 
Chlamydozoa  may  be  nearest  to  them. 

Great  Steps  in  Evolution. — Looking  backwards  we 
see  a  great  succession  of  achievements.  Within  the  realm 
of  the  unicellulars  we  find  every  grade  of  structural  differen- 
tiation— some  relatively  simple,  some  extraordinarily 
complex  like  many  of  the  Radiolarians.  We  can  still 
trace  the  gradual  specialization  of  functions,  the  establish- 
ment of  the  great  types  of  cell  life,  the  beginnings  of  repro- 
duction and  of  death.  One  of  the  earliest  steps  was  the 
dichotomy  which  separated  plants  and  animals — the  most 
momentous  cleavage  in  evolution. 

A  simple  instance  may  serve  to  bring  out  the  point  that 
functions  have  become  more  specialized  as  evolution  pro- 
ceeded. W.  Staniewiez  has  called  attention  to  the  interest- 
ing fact  that  Protozoa  have  never  learned  to  digest  fat. 
All  multicellular  animals  have  this  power,  but  the  Protozoa 
have  not.  Experiments  with  Paramcecium,  Stentor, 
and  some  other  common  Infusorians  show  that  fat  may 
be  ingested,  but  it  is  not  digested.  It  is  not  a  natural 
part  of  a  Protozoon's  food,  and  the  fat  that  is  occasionally 
found  in  natural  conditions  within  the  Protozoon  cell 
seems  to  be  due  to  the  transformation  of  proteids  or  carbo- 
hydrates. If  the  facts  are  correct,  the  power  of  digesting 
fat  was  added  on  to  the  digestive  function  when  the  transi- 


576  THE  WONDER  OF  LIFE 

tion  was  made  from  unicellular  to  multicellular  animals. 

When  certain  simple  organisms,  unable  fully  to  complete 
that  division  into  two  or  more  separate  units  which  normally 
occurs  at  the  limit  of  growth,  began  to  form  multicellular 
'bodies' — one  of  the  greatest  steps  in  evolution  was 
taken.  It  was  perhaps  with  the  acquisition  of  a 
body  that  natural  death  began.  It  was  certainly  with 
the  acquisition  of  a  body  that  there  began  the  very  advan- 
tageous division  of  labour  between  body-cells  and  germ- 
cells.  Among  the  Protozoa  there  are  often  dimorphic 
units  which  combine  in  fertilization  or  conjugation,  and 
they  are  the  analogues  of  the  ova  and  spermatozoa  of  higher 
animals ;  but  it  was  only  after  the  establishment  of  the 
multicellular  body  that  the  sexes,  in  the  strict  sense,  were 
differentiated  as  sperm-producers  and  ovum-producers — 
males  and  females  respectively. 

Another  step  with  far-reaching  consequences  was  the 
replacement  of  the  radial  symmetry  of  polyp  and  jellyfish 
by  bilateral  symmetry.  It  was  some  '  worm  '  types  which 
began  the  useful  habit  of  moving  with  one  end  of  the 
body  always  in  front,  and  with  this  was  associated  the 
acquisition  of  head-brains, — the  beginning  of  the  process 
which  has  led  to  our  being  able  to  tell  our  right  hand  from 
our  left. 

We  think  of  what  was  implied  in  the  discovery  of  an 
oxygen-capturing  respiratory  pigment  like  haemoglobin, 
or  of  an  armouring  substance  like  chitin  which  is  char- 
acteristic of  the  highly  successful  Arthropod  alliance  of 
Crustaceans,  Insects,  Spiders  and  the  like.  The  early 
differentiations  of  striped  muscle  and  specialized  sense- 
organs  were  other  great  events,  and  much  was  gained  by 
such  a  simple  step  as  having  a  food-canal  open  posteriorly 


THE  WONDER  OF  LIFE  577 

and  not  blind,  as  it  was  to  begin  with.  Another  great 
invention  was  the  blood  itself,  a  fluid  tissue,  transporting 
digested  food,  carrying  oxygen  and  carbon  dioxide,  drain- 
ing away  the  nitrogenous  waste,  and  distributing  the 
regulative  hormones  produced  by  organs  of  internal 
secretion. 

Looking  backwards  we  see  that  there  has  been  a  wonder- 
ful twofold  progress — in  differentiation  and  in  integration. 
On  the  one  hand,  bodies  have  become  more  complicated ; 
on  the  other  hand,  more  unified  and  controlled.  In  parti- 
cular, we  see  that  life  has  become  richer  and  freer  as  the 
nervous  system  became  more  complex  and  more  unified. 
A  fresh  start  was  doubtless  made  when  backboned  animals 
emerged,  it  is  difficult  to  say  whence  or  how,  for  with  them 
the  possibilities  of  a  distinctly  higher  life  began,  with  more 
intelligence  and  less  instinct,  with  more  mastery  of  the 
medium.  We  think  of  birds,  of  mammals,  and  of  man ; 
of  the  detailed  colonization  of  the  earth  and  the  exploitation 
of  its  resources ;  and  of  the  consummate  adaptations 
seen  at  every  turn. 

One  of  the  big  impressions  is  the  gradual  emergence  of 
nobler  forms  of  life.  Millions  of  years  passed  before  any 
backboned  animals  appeared.  The  earliest  fossil  fishes 
are  obtained  from  Silurian  strata  ;  the  first  Amphibians 
are  much  later — in  the  Carboniferous ;  the  Reptiles 
probably  began  in  the  Permian ;  the  oldest  known  bird, 
Archseopteryx,  is  Jurassic.  Some  races  reach  their  climax 
and  begin  to  wane,  but  if  we  take  the  Vertebrate  series, 
we  may  say  in  general  terms  that  the  rock-record  reveals 
a  slowly  increasing  perfection. 

To  refer  to  a  concrete  detail,  it  is  strange  to  think  of 
the  fact  that  it  was  not  till  millions  after  millions  of  years 

PP 


578  THE  WONDER  OF  LIFE 

had  passed  that  living  creatures  found  a  voice.  Apart 
from  the  instrumental  noises  of  some  insects,  it  was 
not  until  the  advent  of  Amphibians  in  the  Carboniferous 
age  that  the  silence  of  nature  was  broken  by  any  voice  of 
life.  It  is  useful  to  fix  attention  on  one  race  and  to  note 
what  they  achieved,  and  no  one  surely  can  look  at  the 
fossil  remains  of  the  Carboniferous  Amphibians  without 
a  thrill.  They  are  the  remains  of  pioneers — the  first  back- 
boned animals  to  begin  the  possession  of  the  dry  land, 
the  first  to  have  finger  and  toes  and  thus  the  power 
of  feeling  things  in  three  dimensions,  the  first  to  have  a 
voice  and  a  mobile  tongue,  and  the  first  to  have  true  lungs. 
How  many  acquisitions  these  early  Amphibians  made  ! 

Mr.  W.  D.  Matthew,  of  the  American  Museum  of  Natural 
History,  has  written  appreciatively  concerning  Eryops, 
a  primitive  Amphibian  which  lived  about  the  close  of  the 
Carboniferous  Period — '  five  times  as  old  as  Eohippus  (an 
early  ancestor  of  the  modern  horse),  a  hundred  times  as 
old  as  the  mammoth  or  mastodon  or  the  earliest  known 
remains  of  man'.  It  was  'a  sort  of  gigantic  tadpole  or 
mud-puppy,  with  wide  flat  head,  no  neck,  a  thick  heavy 
body,  short  legs  and  paddle-like  feet  and  a  heavy  flattened 
tail '.  Heavy  and  clumsy,  small- brained  and  slow,  but 
it  was  near  the  top  of  the  genealogical  tree  in  its  day,  and 
it  was  rich  in  promise  !  '  The  giant  dragon-fly  that  darted 
over  the  head  of  the  slow- crawling  Eryops  might  seem, 
except  in  size,  a  far  superior  type  of  being,  a  far  more 
promising  candidate  for  the  position  of  ancestor  to  the 
intelligent  life  which  was  to  appear  in  the  dim  future '. 
But  the  facts  were  far  otherwise.  The  giant  dragon-fly 
had  already  reached  the  limit  of  great  organizational 
change,  while  '  the  amphibian  was  but  beginning  the 


THE  WONDER  OF  LIFE  579 

adaptation  of  the  vertebrate  structure  to  a  terrestrial  life  '. 
It  had  not  circumscribed  its  possibilities,  and  perhaps 
there  is  something  in  Professor  Shaler's  suggestion,  that 
the  possession  of  an  internal  instead  of  an  external  skeleton 
was  a  factor  in  giving  free  play  to  the  evolutionary  potency 
which  lay  concealed  in  these  unpromising  amphibians  of 
the  Carboniferous  forest-swamps. 

The  Fitness  of  the  Environment. — A  favourite  idea 
of  olden  times  was  expressed  in  the  phrase  the  harmony  of 
nature,  the  theory  being  that  the  physical  conditions,  for 
instance,  were  suitable  for  life.  The  universe  was  regarded 
as  distinctly  friendly.  This  idea  has  been  rehabilitated 
in  Professor  Lawrence  J.  Henderson's  recent  essay  on 
The  Fitness  of  the  Environment  (1913),  to  which  we  wish 
briefly  to  refer.  When  a  crust  forms  on  a  heavenly  body, 
like  our  earth,  the  normal  envelope  is  an  atmosphere 
containing  water  and  carbonic  acid  gas,  which  are  necessarily 
and  automatically  formed  in  vast  amounts  by  the  cosmic 
process.  They  are  very  fit  things  in  themselves,  and  fitted 
to  play  an  important  role  in  inorganic  evolution,  but  the 
point  is  that  they  also  exhibit  extraordinarily  great  and 
detailed  fitness  in  relation  to  the  upbuilding  and  susten- 
ance of  living  creatures.  Their  exceptional  properties 
have  contributed  to  the  success  of  life.  There  are  no  other 
compounds  which  share  more  than  a  small  part  of  the 
qualities  of  fitness  which  water  and  carbonic  acid  possess  ; 
and  no  other  elements  which  share  those  of  carbon,  hydro- 
gen and  oxygen.  Living  means  trafficking  with  the  environ- 
ment ;  to  do  this  effectively  organisms  must  be  complex  and 
yet  coherent,  plastic  and  yet  durable ;  and  they  were  able 
to  gain  these  qualities  because  of  the  fundamental  pro- 
perties of  the  primary  constituents  of  the  inanimate  environ- 


580  THE  WONDER  OF  LIFE 

ment.  In  the  same  manner,  the  oceans  which  were  formed 
automatically  in  the  course  of  the  cosmic  process  have  in 
certain  respects  a  maximal  fitness  in  relation  to  life.  Even 
our  own  blood,  which  is  such  an  effective  internal  medium, 
seems  to  owe  some  of  its  virtue  to  Father  Neptune. 

'  The  fitness  of  the  environment  results  from  character- 
istics which  constitute  a  series  of  maxima — unique,  or 
nearly  unique  properties  of  water,  carbonic  acid,  the 
compounds  of  carbon,  hydrogen,  and  oxygen  and  the 
ocean — so  numerous,  so  varied,  so  nearly  complete  among 
all  things  which  are  concerned  in  the  problem,  that  together 
they  form  certainly  the  greatest  possible  fitness.  No 
other  environment  consisting  of  primary  constituents 
made  up  of  other  known  elements  or  lacking  water  and 
carbonic  acid,  could  possess  a  like  number  of  fit  char- 
acteristics or  such  highly  fit  characteristics,  or  in  any 
manner  such  great  fitness  to  promote  complexity,  durability 
and  active  metabolism  in  the  organic  mechanism  which 
we  call  life '....'  In  fundamental  characteristics  the 
actual  environment  is  the  fittest  possible  abode  of  life '. 

It  seems  to  come  to  this  that  ours  is  the  best  of  worlds. 
It  is  certain  that  the  earth  could  not  have  become  the  home 
of  the  living  creatures  that  we  know  unless  it  had  gone 
through  stages  of  chemical  and  physical  preparation. 
It  is  certain  that  the  physical  basis  of  life  as  we  know  it 
could  not  have  been  formed  unless  there  had  been  in 
matter  a  tendency  to  complexify — to  form  atoms,  molecules, 
enormous  molecules,  and  those  unstable  aggregates  of 
molecules  which  we  know  in  colloids.  It  is  also  certain 
that  the  compounds  of  carbon,  with  their  large  molecules, 
and  power  of  colloidal  union,  are  such  as  to  favour  the 
increase  of  structural  complexity,  e.g.,  as  we  see  it  in  the 


THE  WONDER  OF  LIFE  581 

physical  basis  of  life.  And  so  on,  for,  as  Prof.  Henderson 
has  well  shown,  the  evidence  is  cumulative  that  living 
creatures,  as  material  systems,  are  in  no  wise  foreign  to 
the  earth  but  are  in  the  deepest  sense  congruent  with  it. 
This  is  a  very  important  and  sound  conclusion. 

Yet  we  cannot  follow  Prof.  Henderson  to  his  conclusion 
that  '  in  fundamental  characteristics  the  actual  environ- 
ment is  the  fittest  possible  abode  of  life '.  It  may  be  so, 
but  the  assertion  outstrips  the  evidence.  That  we  cannot 
suggest  another  plan  of  evolution,  another  kind  of  make- 
up for  the  physical  basis  of  life,  does  not  by  any  means 
prove  that  there  could  be  no  other,  no  better.  Who  can 
tell  that  there  may  not  elsewhere  be  other  and  fairer  faunas 
and  floras  which  biologists  of  another  and  of  wiser  sort 
rejoice  to  study? 

While  it  is  a  notable  and  valuable  service  to  have  shown 
what  we  may  call  the  solidarity  of  organisms  and  their 
environment,  is  there  not  a  risk  of  arguing  in  a  circle,  and 
making  a  problem  where  none  exists  ?  We  must  remem- 
ber the  old  lady's  fallacy  regarding  rivers  and  towns.  If 
we  grant,  as  Meldola  says,  that  the  elements  have  not  been 
launched  haphazard  into  existence  as  independent  entities  ; 
if  we  admit  a  tendency  in  matter  to  complexify  when  it 
gets  a  chance  (a  tendency  no  more  explicable  than  gravi- 
tation) ;  if  we  suppose,  as  the  author  does,  that '  the  whole 
evolutionary  process,  both  cosmic  and  organic,  is  one ', 
why  should  we  be  surprised  at  the '  two  complementary  fit- 
nesses '  ?  The  characteristic  properties  of  water  and 
carbonic  acid,  of  carbon  compounds  and  colloid  states,  are 
peculiarly  fitted  for  the  life  of  organisms,  because  organisms 
as  mechanisms  (and  our  author  does  not  consider  them 
otherwise)  are  such  as  could  arise  and  survive  and  evolve 


582  THE  WONDER  OF  LIFE 

under  the  given  environmental  conditions.  The  earth  is 
friendly  to  living  creatures  because  in  their  physical 
nature  they  are  bone  of  her  bone,  and  flesh  of  her  flesh — 
her  very  children. 

But  it  is  an  important  piece  of  work  to  have  shown  that 
organisms  cannot  be  thought  of  as  episodically  or  contin- 
gently fitted  to  their  environment,  that  the  '  natural  char- 
acteristics of  the  environment  promote  and  favour  com- 
plexity, regulation,  atid  metabolism,  the  three  fundamental 
characteristics  of  life '.  The  characteristics  that  make 
them  fit  have  contributed  to  the  fitness  of  organisms. 
It  is  no  small  service  to  have  so  clearly  and  circumstantially 
suggested  that  Nature  is  Nature  for  a  certain  purpose. 

The  Method  of  Evolution. — So  far  as  we  know  as 
yet,  the  method  of  organic  evolution  has  been  the  method 
of  trial  and  error :  ceaseless  experimenting  on  the  part  of 
the  germ-cells,  and  the  submission  of  these  tentative  new 
departures  to  that  criticism  by  the  environment,  which 
we  call  Natural  Selection.  The  experiments  are  called 
'  variations ',  and  there  is  a  growing  body  of  evidence 
to  show  that  we  must  distinguish  the  minor  fluctuations 
from  the  major  mutations.  (It  does  not  seem  likely  that 
'  modifications ',  or  the  direct  results  of  peculiarities  of 
nurture  in  the  wide  sense,  are  of  any  direct  importance 
in  evolution,  since  we  have  no  secure  evidence  that  they 
are  ever  transmitted,  as  such  or  in  any  representative 
degree. )  The  facts  in  regard  to  '  mutations  ',  which  we  owe 
to  De  Vries,  Bateson,  and  others,  point  to  the  occurrence 
of  sudden  and  discontinuous  variation ;  '  the  existence, 
that  is  to  say,  of  new  forms  having  from  their  first  beginning 
more  or  less  of  the  kind  of  'perfection  that  we  associate  with 
normality'.  The  general  idea  is  that  novel  characters 


THE  WONDER  OF  LIFE  583 

may  suddenly  appear,  as  it  were,  full-fledged,  with  con- 
siderable perfection  from  the  moment  of  their  emergence, 
and  without  intergrades  linking  them  to  the  parents. 
Furthermore,  the  novel  character  of  the  mutant,  if  we 
may  use  the  word,  is  independently  heritable  and  does  not 
blend  ;  it  can  be  grafted  intactly  on  to  another  stock,  or  it 
can  be  dropped  out  as  such.  Again,  mutations  are  on  the 
whole  qualitative,  as  contrasted  with  the  quantitative 
fluctuations.  It  comes  to  this,  then,  that  the  elusive 
Proteus,  which  is  the  essence  of  every  living  creature,  is 
ever  changeful,  sometimes  leaping  ('  mutations ',  we  call 
the  movements),  sometimes  taking  short  tentative  steps 
('  fluctuations  ',  we  call  them). 

As  to  the  origin  of  fluctuations  and  mutations  we  must 
still  confess  with  Darwin  that  our  ignorance  is  profound. 
Is  it  a  fundamental  characteristic  of  organisms,  that  they 
tend  to  vary  and  often  to  vary  creatively  ?  So  much  must 
be  allowed  for  the  effect  that  fluctuations  in  the  nutritive 
stream  of  the  body  may  have  in  evoking  responsive  changes 
in  the  complex  germ-cells.  So  much  must  be  allowed  for 
the  effect  that  searching  environmental  changes  may  have 
in  acting  as  liberating  stimuli  to  the  germ- cells — pulling 
the  trigger  of  their  potentiality.  So  much  must  be  allowed 
for  the  opportunities  afforded  in  maturation  and  fertiliza- 
tion for  shuffling  the  chromosome  cards,  producing  new 
combinations  or  dropping  out  an  item  altogether. 

Perhaps  we  can  go  a  step  further,  recalling,  for 
instance,  what  Herbert  Spencer  emphasized,  and  what 
the  progress  of  chemistry  since  his  day  has  made  even  more 
vivid,  the  tendency  in  matter  to  complexify — corpuscles 
forming  atoms,  atoms  molecules,  molecules  larger  molecules, 
and  so  on.  Perhaps  the  living  unit,  which  we  know  as  the 


584  THE  WONDER  OF  LIFE 

germ-cell,  utilises  this  complexifying  tendency  in  a  pro- 
gressive differentiation  of  its  own.  Just  as  the  same 
chemical  substance  may  crystallize  in  more  than  one  way, 
so,  but  more  subtly,  the  germ-cell  may  experiment  with 
its  architecture.  The  germ-cell  is  no  ordinary  cell,  it  is 
a  gamete,  a  condensed  individuality ;  and  just  as  an 
intact  organism,  from  Amoeba  to  Elephant,  tries  experi- 
ments, so  it  may  be  that  the  implicit  organism  of  the 
germ-cell  tries  experiments — which  we  call  variations. 
Such  at  least  is  our  view  of  a  great  mystery. 

It  seems,  then,  if  we  are  reading  the  story  of  Evolution 
aright,  that  a  genius  may  be  born  like  Minerva  from  the 
brain  of  Jove.  There  is  brusquely  a  new  pattern,  '  some- 
thing quite  original ',  a  mutation.  It  used  to  be  a  dogma  : 
Natura  non  facit  saltus,  but  evidences  of  Natura  saltatrix 
are  rapidly  accumulating.  They  spoke  of  life  '  slowly 
creeping  upwards  ' — but  the  Proteus  leaps  as  well  as  creeps. 
There  is  doubtless  some  progress  by  thrift,  by  adding  one 
to  one  to  make  a  thousand,  but  it  is  beginning  to  be  clear 
that  Nature  gambles.  The  great  steps  in  evolution  were 
probably  made  by  grands  coups,  not  by  savings.  Many 
of  them  express  new  ideas,  and  it  is  difficult  to  see  how  a 
new  principle  in  organization  could  originate  gradually. 

While  modern  biology  lays  more  emphasis  on  what  may 
be  called  the  ofganismal  factor  in  evolution — what  is 
attainable  by  the  creative  experiments  of  the  organism, 
especially  in  the  germinal  part  of  its  life — this  is  in  no  way 
inconsistent  with  the  Darwinian  theory  of  Natural  Selec- 
tion, or  Nature's  sifting.  The  raw  materials  are  the  inborn 
variations;  the  internal  condition  of  progress  is  their 
heritability  and  their  consistency  with  the  rest  of  the 
organism  ;  the  external  condition  is  the  struggle  for  existence 


THE  WONDER  OF  LIFE  585 

in  its  manifold  forms  ;  the  process  is  discriminate  elimina- 
tion ;  and  the  result  is  the  survival  of  the  variants  fittest 
to  the  given  conditions. 

Eeferring,  for  discussion,  to  our  '  Darwinism  and  Human 
Life,'  we  wish  to  emphasize  what  seems  to  us  of  the  greatest 
importance,  that  Nature's  sifting  is  extraordinarily  mani- 
fold and  subtle,  as  Darwin  always  insisted.  The  struggle 
for  existence  is  much  wider  than  is  suggested  by  the  words 
taken  literally.  It  expresses  the  sum  total  of  the  reactions 
which  living  creatures  make  to  their  limitations  and  diffi- 
culties. We  see  the  struggle  for  existence  wherever  living 
creatures  press  up  against  limiting  conditions ;  wherever 
living  creatures,  with  their  powers  of  growing  and  multiply- 
ing, thrusting  and  parrying,  changing  and  being  changed, 
competing  and  combining,  working  for  self  and  working 
for  others,  do  in  any  way  say,  '  We  will  live '. 

In  the  same  way  the  Natural  Selection  which  Darwin 
spoke  of  metaphorically  as  '  daily  and  hourly  scrutinizing 
throughout  the  world  the  slightest  variations ',  is  only 
thought  of  truly  when  it  is  thought  of  subtly.  For  it 
comprises  all  the  forms  of  discriminate  criticism  which  meet 
the  experiments  or  variations  of  organisms,  now  working 
with  dramatic  swiftness  in  killing  off  unfit  variants  even 
before  they  are  born,  again  working  with  imperceptible 
slowness  giving  to  some  a  slightly  longer  life  or  a  slightly 
larger  family,  now  singling  the  full-grown,  and  again  the 
young,  and  again  the  germ-cells  themselves.  As  Goethe 
said,  '  Nature's  children  are  numberless.  To  none  is  she 
altogether  miserly ;  but  she  has  her  favourites,  on  whom 
she  squanders  much,  and  for  whom  she  makes  great 
sacrifices.  Over  greatness  she  spreads  her  shield'. 

Summary. — Our   view  is   that  the   organism   is  the 


586  THE  WONDER  OF  LIFE 

product — the  creation-result — of  the  germ-plasm  with  its 
great  uniformity  and  yet  ever-newness,  and  the  environ- 
ment with  its  great  uniformity  and  yet  ever-newness. 
The  germ-plasm  is  variable,  that  is  to  say  it  makes  experi- 
ments, some  futile,  like  every  artist's,  some  successful. 
Those  that  are  successful  are  so  because  their  urgent  fingers 
fit  into  the  environmental  glove.  But  this  metaphor  is  on 
one  side  too  static.  For  the  germinal  experiments  that 
succeed  are  those  to  which  the  environment  offers,  as  it 
were,  encouraging  opportunity  for  expression. 

Tactics  of  Nature.— What  we  have  said  in  regard  to 
the  method  of  organic  evolution  refers  only  to  the  general 
formula,  and  we  cannot  here  do  more  than  illustrate  the 
answers  to  the  interesting  further  question  that  arises  as 
to  the  detailed  tactics  in  particular  cases.  The  production 
of  such  geniuses  as  ants  and  bees,  wasps  and  spiders,  rooks 
and  cranes,  elephants  and  horses,  remains  more  or  less 
of  a  mystery.  Though  in  some  cases,  such  as  elephants  and 
horses,  we  have  considerable  information  as  to  the  historical 
stages  of  evolution,  we  have  little  light  in  regard  to  the 
organic  urge  which  may  have  accounted  for  the  successive 
uplifts.  As  has  been  said,  we  understand  the  survival 
but  not  the  arrival  of  mutations.  It  is  different,  however, 
when  we  turn  to  Nature's  method  of  making  extraordinarily 
new  things  out  of  very  old  things.  For  this  is  what  has 
happened  in  a  great  number  of  cases  where  something 
apparently  novel  has  emerged.  The  old  is,  as  it  were,  re- 
crystallized.  The  mineral  becomes  a  jewel.  Let  us  give 
a  few  illustrations. 

The  spinnerets  of  a  spider  are  very  novel  contrivances, 
but  they  apparently  represent  transformed  limbs.  The 
butterfly's  spiral  proboscis  is  a  coiled  jaw  and  the  bee's 


THE  WONDER  OF  LIFE  587 

sting  an  elaborated  ovipositor.  The  serpent's  fangs  are 
folded  or  channelled  teeth,  and  the  reservoirs  of  venom  are 
but  specialized  salivary  glands.  The  milk-glands  of  mam- 
mals seem  to  have  arisen  from  clusters  of  sebaceous  skin- 
glands,  common  to  both  sexes.  Every  schoolboy  knows 
that  the  elephant's  trunk — an  extraordinary  novelty  in 


FIG.  92. — Wing  of  Adelie  Penguin,  Pygoscelis  adelise,  illustrating  the 
fact  that  a  very  novel  structure,  a  nipper,  may  arise  by  a  not  very 
great  transformation  of  an  older  structure — a  whig.  (After  Pycraft. ) 
A,  the  entire  wing  covered  with  small  flat  feathers  ;  B,  the  bones  of 
the  wing  ;  H,  humerus  ;  R,  radius  ;  u,  ulna  ;  R,  radiale,  one  of  the 
two  free  wrist  bones  ;  u,  ulnare,  the  other  free  wrist  bone  ;  CMC, 
carpometacarpus,  part  of  wrist  and  palm  fused ;  I,  thumb  bone 
fused ;  II,  second  digit  with  two  joints  or  phalanges  ;  III,  third 
digit  with  one  joint  (PH.  i.). 

its  day — is  just  the  creature's  nose,  and  every  student  of 
comparative  anatomy  can  tell  us  how  the  hammer  and 
anvil  that  form  part  of  the  delicate  apparatus  for  conveying 
vibrations  to  the  inner  ear  were  once  part  and  parcel  of  the 
rougher  and  more  commonplace  mechanism  of  the  jaws. 
There  is  no  doubt  that  to  make  an  apparently  very  new 
thing  out  of  a  really  very  old  thing  is  part  of  Nature's  magic 


588  THE  WONDER  OF  LIFE 

The  idea  which  we  have  illustrated  was  clearly  expressed 
by  Dr.  Anton  Dohrn,  the  founder  of  the  famous  Zoological 
Station  at  Naples.  He  called  it '  the  principle  of  function- 
change  ',  and  showed,  for  instance,  that  the  unimportant 
bladder  which  grows  out  from  the  hind  end  of  the  gut  in 
frogs,  becomes  an  all-important  birth- robe,  the  allantois 
in  reptiles  and  birds,  and  part  of  the  placenta,  which 
binds  the  unborn  young  to  the  mother,  in  mammals. 

New  things  out  of  old,  that  is  the  law.  For  what  could 
have  been  newer  in  its  day  than  a  feather,  and  what  is  a 
feather  but  a  glorified  scale  ?  In  regard  to  this  homology, 
which  Aristotle  discerned  so  long  ago,  there  is  still  a  little 
difficulty,  for  the  development  of  a  feather  is  very  distinc- 
tive and  in  several  respects  unlike  that  of  a  scale.  And 
there  are  no  transitional  types  between  scale  and  feather, 
the  minute  flat  structures  on  a  penguin's  flippers  being  no 
nearer  scales  than  are  the  plumes  of  an  eagle.  Recent 
investigations,  such  as  Frieda  Bornstein's  study  of  the 
foot  of  the  capercaillie,  where  feathers  and  scales  occur  in 
close  association,  point  to  the  conclusion  that  a  feather 
corresponds  not  to  a  whole  scale,  but  to  part  of  a  scale, 
another  part  being  suppressed.  But  none  the  less  the 
feather  illustrates  the  evolution  of  the  new  from  the  old. 

As  another  illustration  of  tactics  we  would  briefly  refer 
to  the  idea  of  temporal  variations  which  has  been  expounded 
by  Professor  Patrick  Geddes.  In  the  chapter  on  '  The 
Cycle  of  Life  '  we  have  spoken  of  the  changes  which  may 
come  about  by  lengthening  out  one  chapter  of  the  life- history 
and  compressing  another,  by  altering,  as  it  were, '  the  time  ' 
of  the  tune  at  different  periods.  It  seems  that  we  can 
interpret  not  a  few  evolutionary  changes  in  the  light 
of  this  idea.  For  some  types  are  all  youth,  and  others 


THE  WONDER  OF  LIFE  589 

are  born  old ;  some  telescope  adolescence  and  others  draw 
it  out  for  many  years.  It  is  plausible,  and,  as  we  say, 
suggestive,  to  regard  certain  types  as  arrested  juveniles 
and  others  as  precociously  senile,  just  as  we  have  plants 
which  remain  as  great  buds  and  others  which  are  all  flower. 

The  idea  is  the  more  valuable  because  we  know  of  an 
agency  in  higher  animals  by  which  the  rate  of  development 
of  particular  parts  can  be  altered.  It  has  been  shown 
that  internal  secretions  have  a  regulating  action  on  the 
growth  of  parts  of  the  body.  Some  act  as  accelerants, 
others  as  inhibitors.  It  is  said  that '  infundibular  extract 
(from  the  pituitary  body)  has  been  employed  with  success 
in  recent  years  in  order  to  add  in  a  short  time  a  few  desirable 
inches  to  a  young  man's  height.  So  that  it  seems,  after 
all,  as  if  one  may,  by  taking  sufficient  thought,  add  a  cubit 
to  one's  stature.  In  other  cases,  it  is  the  absence  of  a 
specific  secretion  that  causes  some  particular  part  to  grow 
abnormally  large,  as  if  some  brake  were  removed.  Prof. 
Arthur  Dendy  has  suggested  that  this  internal  regulation 
of  growth  may  account  for  cases  where  animals  or  parts 
of  animals  seem  to  have  acquired  some  sort  of  momentum, 
growing  far  beyond  the  limit  of  utility.  A  disappearance 
of  certain  glands,  or  some  change  in  the  secretion  of  certain 
glands,  may  remove  the  normal  brake,  with  the  result 
that  a  part  which  was  wont  to  be  controlled  as  to  its 
growth  by  a  specific  secretion  or  '  hormone ',  may  grow 
far  beyond  its  optimum,  and  may  indeed  become  fatal  to 
its  possessor. 

Another  theory,  deserving  of  more  than  brief  illustration , 
is  suggested  by  Virchow's  idea  of  an  optimism  of  pathology. 
Certain  organic  diseases  are  due  to  constitutional  variations 
which  tend  to  the  wrong  side  of  viability,  but  those  germi- 


5go  THE  WONDER  OF  LIFE 

nal  variations  that  miss  are  not  far  removed  from  those 
that  hit,  and  what  misses  in  one  type  may  hit  the  mark  in 
another.  Constitutional  disease  is  metabolism  which 
has  got  out  of  time,  out  of  place,  and  out  of  proportion. 
What  is  disease  in  one  organism  may  be  normalized  in 
another.  Let  us  give  examples. 

The  strange  process  by  which  the  bone  at  the  base  of 
the  stag's  antlers  dies  away  every  year  would  be  a  patho- 
logical necrosis  in  other  animals,  but  it  has  been  normalized 
in  deer  and  allows  the  antlers  to  fall  off.  The  remarkable 
changes  that  occur  in  Ascidian  larvae  or  in  tadpoles' 
tails  at  the  time  of  metamorphosis  would  certainly  be 
classed  as  pathological  degenerative  processes  in  other 
types,  but  they  have  been  normalized.  Similarly,  the 
metamorphosis  from  the  larval  to  the  adult  type  of  archi- 
tecture is,  in  many  insects,  accompanied  by  inflammatory 
crises  in  which  phagocytes  play  an  important  role.  The 
viscid  threads  by  means  of  which  the  male  stickleback 
binds  together  the  leaves  of  plants  to  make  a  nest  are  pro- 
duced, according  to  Mobius,  by  the  enlarged  testes  affect- 
ing the  kidneys  in  a  semi- pathological  manner.  There 
are  parallel  pathological  products  in  higher  animals,  but  in 
the  stickleback  the  process  has  been  normalized,  and 
turned  to  good  account.  Do  not  the  sea-swifts,  which 
make  snow-white  nests  of  the  copious  secretions  of  the 
mouth,  suffer  from  super-salivation,  and  what  shall  we  say 
of  the  '  pigeon's  milk '  which  is  formed  from  a  curious 
degeneration  and  disruption  of  the  cells  lining  the  crop  ? 

In  further  illustration  of  this  normalizing  of  the  patho- 
logical, we  may  refer  to  Poyarkoff's  description  of  the 
gill-plate  sacs  in  which  the  embryos  of  the  common  fresh- 
water bivalve,  Cyclas,  are  incubated.  The  embryos 


THE  WONDER  OF  LIFE  591 

develop  in  the  shelter  of  the  inner  gill-plate  within  little 
sacs,  and  the  point  is  that  these  are  in  the  main  due  to  the 
activity  of  leucocytes.  In  other  words,  they  arise  by  a 
process  analogous  to  inflammation.  After  the  embryos 
are  liberated  the  gill- plate  requires  considerable  patching 
up,  especially  as  regards  its  epithelial  covering. 

TRADING  WITH  TIME 

In  a  preceding  chapter  we  gave  illustrations  of  life's 
victory  over  difficulties.  The  most  uninviting  corners  of 
the  earth  and  sea  are  explored  and  exploited ;  the  most 
unpromising  habitats  become  comfortable  homes ;  a 
table  is  spread  in  the  wilderness ;  there  is  sometimes,  as 
we  have  seen,  an  amazingly  successful  recklessness,  and 
in  cases  like  the  migratory  birds  who  literally  '  know  no 
winter  in  their  year ',  we  are  face  to  face  with  an  achieve- 
ment which  seems  not  far  short  of  getting  the  better  of 
Time. 

(A)  Registering  Experience. — The  beginning  of  the 
organism's  business  of  trading  with  time  was  not  far  from 
the  beginning  of  living  organisms  themselves.  We  are  not 
sure  that  a  living  creature  was  worthy  of  the  name  until 
it  became  able  to  register  its  experience,  until  it  was 
able  to  profit  by  what  happened  to  it.  They  say  that  the 
bar  of  iron  once  struck  remembers  the  blow,  which  seems 
to  us  rather  an  abuse  of  metaphor,  but,  as  we  believe  in 
the  value  of  metaphor  as  a  scientific  instrument,  we  do 
not  press  our  objection.  We  would  ask,  however,  whether 
the  smitten  bar  of  iron,  or  the  jarred  crystal,  or  the  jewel 
whose  sanctity  was  violated,  remembers  the  experience 
to  its  own  advantage,  for  that  is  what  the  organism  does. 
Its  premiums  paid  to  experience  are  its  own  best  treasures. 


592  THE  WONDER  OF  LIFE 

This  capacity  of  registering  experience  and  of  utilizing 
that  registration  in  subsequent  activities,  appears  to  us 
to  be  of  the  very  essence  of  life.  To  take  an  instance  that 
seems  simple,  though  it  is  probably  very  difficult,  they  say 
that  Venus's  Fly  Trap  (Dioncea  muscipula)  when  it  has  been 
tricked  several  times  in  succession  by  stimuli  which  bring 
it  no  satisfaction  (or  which  do  not  lead  on  to  the  normal 
sequences  to  which  the  plant  has  been  habituated  in  Nature), 
will  cease  to  respond  to  the  provocative  stimuli.  It  passes 
into  a  state  of  '  physiological  sulks '  ;  it  becomes  callous 
to  stimuli ;  and  this  is  the  very  best  thing  it  could  do, 
short  of  catching  hold  of  the  tantalizing  experimenter. 
It  almost  remembers. 

It  must  be  recognized  that  among  the  simpler  animals, 
such  as  Protozoa,  Sponges,  Zoophytes,  Sea-Anemones, 
Corals,  Jellyfishes,  Sea-Urchins,  Starfishes,  and  simple 
Worms,  with  not  very  much  in  the  way  of  what  are  popu- 
larly called  '  habits  ',  there  is  great  sensitiveness  to  stimulus 
and  a  remarkable  power  of  somehow  registering  experiences. 
A  starfish  has  no  nerve-centres  or  ganglia  at  all ;  that  is  to 
say,  the  nerve  cells  of  its  nervous  system  are  not  concen- 
trated, and  indeed  they  have  not  sunk  beneath  the  level 
of  the  skin ;  but  the  starfish  has  a  remarkable  power  of 
registering  experiences  and  acting  differently  because  it 
does  so.  It  has  got  far  above  the  level  of  simply '  answering 
back '.  One  reaches  a  higher  level,  of  course,  when  there 
is  real  and  effective  memory,  for  we  cannot  believe  in  more 
than  vague  memory  in  creatures  that  have  not  nerve- 
centres.  For  real  and  effective  memory  there  must  be 
repositories  or  treasure-houses,  such  as  nerve-centres 
afford. 

(B)  Individual  Modifications,— We  see  then  that  the 


THE  WONDER  OF  LIFE  593 

organism  has  a  characteristic  power  of  registering  experi- 
ences, and  the  next  step  in  our  argument  is  that  these 
experiences  may  have  lasting  effects.  Let  us  take  one 
illustration  from  the  results  of  imprisonment  in  darkness. 
Light,  as  every  one  knows,  has  many  effects  on  the  living 
creature  : — it  is  used  by  the  green  leaf  in  building  up  organic 
substances ;  it  makes  our  pulse  beat  more  quickly ;  it 
serves  as  a  liberating  stimulus  for  the  development  of  pig- 
ment. These  are  only  three  of  the  many  relations  between 
light  and  life.  We  inquire  therefore  with  interest  into  the 
negative  side — the  influence  of  darkness,  and  we  shall 
refer  to  Ogneff's  very  interesting  experiments  on  gold-fishes. 
He  kept  them  in  a  roomy  tank  and  with  plenty  to  eat — 
earthworms  and  '  blood- worms '  (larvae  of  Chironomus, 
the  harlequin  fly) — but  in  absolute  darkness.  He  kept 
this  up  for  over  three  years,  and  observed  the  modifications 
that  occurred  in  the  fish. 

The  colour  first  became  black,  but  in  the  second  year 
it  became  golden  again,  and  the  reason  for  this  is  interest- 
ing. To  begin  with,  the  dark  pigment-cells  (melanophores) 
spread  out  and  covered  up  the  subjacent  layer  of  waste- 
crystals  (iridocytes)  which  give  the  gold  fish  its  golden 
sheen.  But  subsequently  the  wandering  amoeboid  cells 
or  phagocytes  devoured  the  dark  pigment- cells  and  thus 
re- exposed  the  golden  layer. 

The  changes  in  the  eye  were  even  more  interesting. 
A  complete  alteration  occurred  in  the  structure  of  the 
pigment-  epithelium  of  the  eye,  and  there  was  a  complete 
disappearance  of  the  rods  and  cones,  and  of  some  other 
characteristic  features  of  the  eye.  Profound  atrophy 
of  the  eye  occurred  in  the  absence  of  any  functioning,  and 
the  fish  became  totally  blind.  This  experiment  is  of  great 

Q  Q 


594  THE  WONDER  OF  LIFE 

interest,  and  it  should  be  repeated  by  some  other  investi- 
gator on  some  other  type.  It  shows  us  how  much  may 
happen  in  an  individual  lifetime.  It  suggests  that  an 
individual  fish  imprisoned  in  a  perfectly  dark  cave  would 
become  blind.  In  the  next  generation  the  atrophy  of  the 
eye  would  probably  be  greater,  since  the  offspring  would 
experience  the  darkness  from  birth  while  their  parents 
experienced  it  only  from  the  date  of  imprisonment.  It  is 
likely  that  the  absence  of  light-stimulus  would  inhibit  the 
development  of  the  eye.  Thus  blind  fishes  in  caves  might 
be  accounted  for  in  terms  of  individual  loss  through  disuse. 
If  the  degeneration  of  the  eye  continued  to  increase  after 
the  second  generation,  that  would  prove  the  hereditary 
accumulation  of  an  acquired  character.  On  another 
theory,  blindness  might  arise  in  caves  as  a  germinal 
variation  and,  being  possibly  advantageous,  become 
a  racial  character.  A  constitutionally  blind  race  would 
not  show  any  power  of  getting  back  its  well- developed 
eyes  on  re- exposure  to  light,  but  a  modificationally  blind 
race  would. 

A  drastic  change  in  the  surroundings  often  makes  the 
organism  quiver  in  its  inmost  parts,  and  curious  modifi- 
cations, that  we  do  not  as  yet  know  the  meaning  of,  are 
brought  about.  Thus  Ogneff  has  shown  that  Axolotls 
kept  in  darkness  and  starved  at  the  same  time  become 
blanched — an  experiment  which  may  throw  some  light 
on  the  whiteness  of  some  cave  animals,  such  as  the  Proteus 
of  the  Carinthian  caves.  In  the  Axolotls  the  black  pig- 
ment cells  atrophied  and  were  destroyed  by  the  ever- ready 
body-guard  of  phagocytes,  which  carried  off  the  pigment. 
This  goes  on  not  only  in  the  skin,  but  in  some  of  the  internal 
organs,  which  also  lose  their  black  pigment- cells. 


THE   WONDER  OF   LIFE  595 

(C)  Habituation. — What  is  true  of  the  results  of  environ- 
mental influence  holds  good  in  regard  to  function.     A 
sequence  of  activities  often  performed  leads  to  the  estab- 
lishment of  a  habit,  which  is  associated  with  a  structural 
change  in  the  nervous  system.     As  we  say,   paths  are 
established  along  which  nervous  messages   pass  swiftly 
and  smoothly.    Experiments,  such  as  some  of  those  alluded 
to  in  the  chapter  on  "  The  Ways  of  Life,"  show  clearly  that 
the  individual  organism  can  in  various  degrees  become 
habituated,  and  it  is  plainly  advantageous  to  it  to  have 
engrained    reactions,    tropisms,    rhythms    and    instincts. 
Ready-made    effective    answers    to    frequently    recurring 
questions  save  time  and  energy,  and  often  the  life  of  the 
creature.     In  many  cases  there  is  no  time  for  experiment- 
ing or  deliberating,  the  answer  must  be  instantaneous  if 
it  is  to  be  any  good  at  all.    But  this  brings  us  to  the  difficult 
fact  that  it  is  often  with  more  than  individual  habituation 
that  the  organism  gives  its  ready-made  answer — such  as 
passing  into  hibernation  on  the  approach  of  winter,  or 
flying  south  in  the  autumn.     Antecedent  to  its  individual 
experience,  it  exhibits  the  effective  reaction. 

(D)  Transmissibility    of    Acquired    Characters. — 
In  the  case  of  a  Protozoon,  such  as  an  Amoeba  or  a  Slipper 
Animalcule,  the  problem  is  simple.  The  unicellular  creature 
gathers  experience ;  its  organization  is  definitely  affected  ; 
it  has  learned  a  lesson.     This  is  not  for  itself  alone  but  for 
its  race,  for  it  multiplies  by  dividing  into  two,  and  each 
of  the  daughter- cells  shares  in  the  organization  which  has, 
so  to  speak,  learned  a  lesson.     Each  new  unit  can  then  go 
on  to  learn  the  lesson  a  little  better,  and  so  we  have  the 
rudiments  of  behaviour  in  these  relatively  simple  living 
creatures.     There  is  no  doubt  here  that  the  race  profits 


596  THE  WONDER  OF  LIFE 

by  the  premiums  which  the  individuals  pay  to  experience. 

But  when  we  pass  from  the  unicellulars  to  the  multicellu- 
lars  the  problem  changes.  There  is  a  differentiation  be- 
tween body-cells  and  germ-cells,  and  although  the  germ- 
cells  do  not  live  a  charmed  life  within  the  body  it  is  difficult 
to  suppose  that  experiences  registered  in  the  body  can 
affect  the  germ-cells  in  such  a  specific  and  representative 
way  that  the  offspring  will  profit  by  the  experiences  of  its 
parent's  body.  It  is  possible  that  deeply  saturating 
environmental  influences  may  affect  both  body  and  repro- 
ductive organs  somewhat  similarly.  It  is  possible  that 
very  important  and  frequently  recurrent  alterations  of  the 
ordinary  metabolism,  which  are  registered  as  structural 
modifications  of  the  body,  may  sometimes  be  associated 
with  the  formation  of  characteristic  cellular  substances 
which  saturate  through  the  body  and  pass  into  the  germ- 
cells.  Through  the  germ-cell  when  it  comes  to  develop, 
these  hypothetical  substances  may  affect  the  body  of  the 
offspring.  In  point  of  fact,  however,  we  do  not  at  present 
know  that  a  structural  modification  of  the  body  of  the 
parent,  impressed  from  without  by  some  peculiarity  of 
the  environment,  or  brought  about  through  some  peculiarity 
of  functioning,  can  affect  the  offspring  in  such  a  specific 
or  representative  way  that  the  parent's  modification  is 
transmitted.  We  do  not  know  that  this  ever  occurs. 

Many  thoughtful  people  find  it  impossible  to  believe 
that  somatic  experiences  do  not  specifically  or  representa- 
tively affect  the  offspring.  How  can  there  be  any  trading 
with  time  worth  talking  about  if  the  individual  gains  are 
not  handed  on  as  a  legacy  to  the  offspring  ?  But  the 
confidence  with  which  this  question  is  asked  sometimes 
disappears  when  we  ask  another — '  And  the  losses  too  ?  * 


THE  WONDER  OF  LIFE  597 

For  that  would  be  obviously  very  disadvantageous,  and  yet 
we  cannot  have  the  one  without  the  other,  the  pluses 
without  the  minuses. 

All  biologists  are  agreed  that  starving  a  mother  may 
prejudice  the  development  of  the  offspring,  and  that  the 
accumulation  of  toxins  in  the  body  of  either  parent  may 
have  the  same  effect,  but  that  is  not  the  point  of  the  long- 
continued  and  still  unended  controversy  regarding  the 
transmission  of  somatic  modifications  (badly  called  '  the 
inheritance  of  acquired  characters ').  The  precise  point 
at  issue  is  this :  Does  a  structural  change  in  a  part  of  the 
body,  directly  induced  by  use  or  disuse,  or  by  some  change  in 
surroundings  and  nurture  generally,  ever  affect  the  germ- 
plasm  in  the  reproductive  organs  in  such  a  specific  or  repre- 
sentative way  that  the  offspring  will  thereby  exhibit  the  same 
modification  that  the  parent  acquired,  or  even  a  tendency 
towards  it  ? 

We  have  discussed  this  question  carefully  in  our  Hered- 
ity and  Darwinism  and  Human  Life ,  and  we  shall 
not  attempt  to  summarize  the  pros  and  cons.  It  may  be  of 
interest,  however,  to  give  a  short  account  of  what  appears 
to  us  to  be  the  most  careful  experimental  contribution 
that  has  yet  been  made  towards  the  solution  of  this  crucial 
biological  problem.  We  refer  to  Dr.  W.  E.  Agar's  experi- 
ments on  one  of  the  small  Crustacea,  a  Daphnid  or 
water-flea.  The  condensed  narrative  is  necessarily  a 
little  difficult,  but  it  will  reward  the  serious  student,  not 
only  in  its  interesting  conclusion,  but  also  as  a  fine 
example  of  scientific  method. 

(E)  A  Test  Case.— Dr.  W.  E.  Agar  studied  a  curious 
abnormality — reflexion  of  the  valves  of  the  carapace — in 
the  water-flea  or  Daphnid,  called  Simocephalus  vetulus. 


598  THE  WONDER  OF  LIFE 

The  abnormality  seems  to  be  induced  by  the  nature  of 
the  food  ingested.  Affected  animals  appear  quite  healthy 
and  reproduce  freely.  He  found  that  although  individuals 
were  removed  to  control  conditions  (of  relative  normality) 
before  the  eggs  were  laid,  the  young  developing  from  these 
eggs  exhibit  the  same  abnormality  as  that  which  their 
parents  had  acquired  during  their  lifetime,  as  a  direct 
result  of  their  environment.  This  result  has  been  con- 
firmed over  and  over  again.  Females  with  ripe  eggs  were 
also  removed  from  control  conditions  and  put  into  the 
particular  culture  which  induces  reflexion  of  the  valves. 
The  young  developed  from  these  eggs  were  fully  normal, 
showing  the  persistence  of  the  effects  of  normal  environ- 
ment. Subsequent  broods  of  these  females  in  the  culture 
became  successively  more  and  more  reflexed,  i.e.  the 
normality  wore  off  just  as  the  abnormality  also  does. 

In  a  second  set  of  experiments  by  raising  the  temperature 
(to  28-5°— 31-5°C.)  the  size  of  the  young  Daphnids  was 
greatly  reduced  in  their  first,  and  indeed  in  all  stages.  The 
rate  of  the  life- cycle  was  also  enormously  increased,  the 
period  from  the  birth  of  the  parent  to  the  birth  of  the 
young  being  fourteen  days  at  16°  and  six  days  at  30°. 
The  number  of  young  per  brood  was  diminished.  The  im- 
portant results  of  the  experiment  were  the  following.  The 
specimens  developing  from  eggs  laid  by  parents  a  few  hours 
after  removal  from  the  higher  to  the  lower  temperature 
were  almost  as  small  as  those  born  at  the  higher  temperature. 
The  subsequent  eggs  laid  by  the  same  parents,  still  under 
control  conditions,  still  remained  affected  by  the  smalhiess- 
producing  conditions,  though  to  a  rapidly  diminishing 
extent. 

In  a  third  set  of  experiments  a  reduction  of  length  was 


THE  WONDER  OF  LIFE  599 

caused  by  living  in  a  particular  kind  of  solution.  The 
reduction  was  found  to  persist  for  a  short  time,  and  was 
followed  by  a  reaction. 

The  experiments  illustrate  '  parallel  induction.'  In  the 
first  and  second  sets  of  experiments,  at  any  rate,  individuals 
placed  in  abnormal  environments  in  their  first  stage 
acquired  the  definite  abnormal  features  in  their  own  bodies 
in  later  stages.  Simultaneously,  the  eggs  in  their  ovaries 
were  influenced  in  such  a  way  that  the  young  developed 
from  them  presented  at  birth  the  same  abnormality  as 
that  which  their  parents  had  acquired  in  their  lifetime. 
It  made  little  difference  whether  the  young  developed 
from  eggs  laid  after  removal  of  the  parents  to  control 
conditions,  or  were  bom  in  the  abnormal  environment, 
so  long  as  the  eggs  underwent  their  ovarian  growth  while 
the  parents  were  under  the  influence  of  the  environment. 
In  the  subsequent  broods  of  those  parents  which  had  been 
removed  to  control  conditions  the  effect  of  the  abnormal 
conditions  appeared  in  rapidly  diminishing  intensity.  In 
the  second  generation  in  control  conditions  the  abnormal 
effect  still  persisted  (in  the  first  two  sets  of  experiments), 
but  to  a  very  slight  degree.  In  all  three  sets  of  experiments 
a  very  decided  reaction  appeared  in  the  third  generation. 

Mutations,  giving  rise  to  new  types,  are  due  to  a  change 
in  the  composition  in  the  living  unit.  '  The  other  cause 
of  variation — a  change  in  the  environment  while  the  living 
units  remain  the  same — is  probably  far  commoner.  Such 
a  change,  if  effective,  will  probably  result  in  the  formation 
of  unusual  metabolic  products  included  in  the  living  proto- 
plasm, and  thus  the  visible  external  variation  produced 
may  have  as  its  immediate  cause  either  the  changed  environ- 
ment itself,  or  the  altered  protoplasmic  inclusions.  In 


6oo  THE  WONDER  OF  LIFE 

the  case  of  parallel  induction,  it  seems  that  the  environ* 
ment  works  indirectly,  through  the  mediation  of  these 
(not  living)  products,  which  when  once  formed  are  not 
immediately  got  rid  of,  but  are  passed  on  passively  included 
in  the  protoplasm  of  the  gamete '.  Some  (not  living) 
product  is  included  in  the  egg,  passes  passively  into  the 
body  which  develops  from  the  egg,  and  thus  produces  on 
the  body  the  same  effect  as  it  produced  on  the  body  of  the 
parent  which  acquired  the  character  in  question. 

Dr.  Agar  sums  up  the  question  of  transmissible  environ- 
mental effects  as  follows: — (1)  A  changed  environment 
(in  its  widest  sense)  may  produce  a  visible  modification  in 
the  body  indirectly  by  altering  the  nature  of  the  metabolic 
products  included  in  the  living  protoplasm.  These  in 
turn  react  with  the  protoplasm,  and  therefore  effect  changes 
in  its  product,  the  body.  (2)  Whenever  the  environment 
acts  simultaneously  on  body  and  gonad  a  similar  alteration 
in  metabolic  inclusions  of  somato-  and  germ-plasm  takes 
place.  (3)  These  metabolic  substances  included  in  the 
germ-cell  naturally  pass  into  the  developing  body,  which, 
therefore,  shows  the  same  modification  as  its  parent  did, 
even  though  removed  from  the  environment  in  question. 
(4)  These  substances  may  produce  a  powerful  effect,  though 
present  only  in  minimal  quantities.  (5)  They  may  be  of 
such  a  nature  as  to  stimulate  the  formation  of  antibodies, 
thus  causing  a  reaction  in  later  generations. 

It  is  probable  that  many  biologists  of  to-day  would  be 
relieved  to  find  that  there  is  much  more  truth  in  Lamarckism 
than  Charles  Darwin  thought  there  was  when  he  said  '  Hea- 
ven forfend  us  from  such  Lamarck  nonsense '.  We  have 
taken  the  most  scientific  investigation  we  know  of  that 
bears  on  this  question,  and  it  does  not  seem  to  strengthen 


THE  WONDER  OF  LIFE  601 

the  Lamarckian  position.  It  is  easy  to  interpret  results 
as  due  to  the  hereditary  accumulation  of  individual  gains 
and  losses,  which  have  been  acquired  under  conditions 
of  changed  function  or  changed  environment ;  but  when 
it  comes  to  experimental  testing  the  case  breaks  down. 

(F)  Does  Experience  count  for  the  Race  ? — Let  us 
turn  back  to  our  study  of  instincts,  with  this  extremely 
important  question  in  our  minds.     It  is  certain  that  many 
animals  have  an  inborn  capacity  of  reacting  in  a  definite 
and  adaptive  way  to  particular  stimuli,  and  a  succession 
of  these  reactions  may  be  linked  together  in  a  very  effective 
piece  of  behaviour.     In  some  cases  at  least,  as  we  sought 
to  show,  it  is  possible  to  give  a  reasonable  interpretation  of 
these  instinctive  capacities.     We  can  think  of  them  be- 
ginning as  germinal  variations ;    we  can  think  of  them 
progressing  as  germinal  variations ;   we  can  think  of  them 
being  most  subtly  perfected  in  the  course  of  Natural  Selec- 
tion.    All  this  is  outside  of  the  hypothesis  that  the  tutelage 
of  experience  counts  for  anything  except  in  the  individual 
lifetime.     That  individual  experience  may  give  a  finishing 
touch  to  instinctive  capacity  may  be  admitted  without 
accepting  the  view  that  these  individual  gains  are  in  any 
representative  way  transmissible. 

What  we  have  stated  is  the  ordinary  Darwinian  view, 
but  we  must  in  fairness  give  a  statement  of  the  Mnemic 
interpretation,  according  to  which  the  offspring  are  sup- 
posed to  benefit  directly  by  the  premiums  paid  to  experi- 
ence on  the  part  of  their  parents  and  ancestors. 

(G)  Mnemic  Theories. — The  term   '  mnemic ',  which 
recalls  the  more  familiar  word  mnemonic,  is  applied  to  the 
theories  of  heredity  suggested  by  Ewald  Hering,  Samuel 
Butler,  Richard  Semon  and  others,  according  to  which 


602  THE  WONDER  OF  LIFE 

the  germ-cells  are  supposed  to  treasure  up  some  of  the 
results  of  the  organism's  experience,  as  it  were,  by  uncon- 
scious memory,  so  that  when  they  come  to  develop  they 
reproduce  in  some  measure  the  traits  which  their  parents 
or  their  ancestors  acquired  as  the  result  of  experience. 
The  idea  is  that  the  germ-cells  become  stored  with  the 
latent  '  memories  '  of  past  generations,  or  less  metaphoric- 
ally that  the  germ- cells  are  changed  or  impressed  in  a 
^definite  and  specific  way  by  the  organism's  experiences. 
Development  is  in  part  the '  recollection  '  of  these  germinally 
treasured  *  memories '. 

Samuel  Butler's  view  was  that  an  inheritance  implies 
;  a  store  of  memories  and  that  development  is  akin  to  recol- 
lection. A  newly  hatched  chick  pecks  at  once  and  with 
good  effect,  because  certain  cells  in  the  chick  remember 
having  superintended  pecking  before.  Part  of  every  in- 
dividual existed  before  in  the  parents  and  the  molecules 
have  a  memory  of  previous  experiences. 

Let  us  take  as  a  very  interesting  illustration  E. 
Bordage's  observations  on  European  peach  trees  trans- 
ported to  Reunion.  As  has  been  noticed  in  similar  cases, 
they  dropped  their  deciduous  habit  and  became — it  took 
some  twenty  years — evergreen.  The  individual  constitu- 
tion was  altered.  But  the  still  more  interesting  point 
is  that  when  seeds  of  these  pseudo-evergreens  were  sown 
in  certain  mountainous  districts  with  a  considerable 
amount  of  frost,  they  produced  young  peach  trees  which 
were  also  evergreen.  European  seeds  sown  in  similar 
places  produced  ordinary  deciduous  trees. 

It  must  not  be  hastily  concluded  that  an  interesting 
case  like  this  compels  us  to  return  to  the  old  belief  in  the 
transmission  of  acquired  characters — in  the  form  that 


THE  WONDER  OF  LIFE  603 

belief  took  before  Weismann's  scepticism.  The  change 
to  evergreenness  was  physiological  rather  than  structural 
— a  change  in  the  rhythm  of  metabolism"perhaps.  More- 
over it  is  quite  likely  that  the  climatic  change  operating 
for  many  years  influenced  the  germ-cells  of  the  peach  along 
with  the  whole  tree.  This  is  a  legitimate  theoretical  dis- 
tinction, though  it  is  not,  perhaps,  of  much  practical  im- 
portance. 

Let  us  try  to  state  Semon's  central  position  without 
using  his  somewhat  bewildering  terminology.     Every  one 
admits  that  an  organism  reacts  to  many  different  kinds 
of  external  change.     It  registers   within   itself   its  novel 
experiences.     Some   of   these   produce   changes   in   what 
Semon  calls  the  '  energetic  sJtuajilQi}  '  of  the  whole  organism,  \^ 
and  these  are  supposed  to  impress  themselves  in  a  lasting 
way  on  the  germ-cells.     The  impressed  effects  on  the  germ-  -1 
cells  are  conveniently  called  '  engrams '.   Just  as  our  mind  ) 
becomes  rich  in  memories  of  experiences,  so  the  germ- plasm  .. 
becomes  stored  with  many  '  engrams '. 

The  second  general  idea  in  Semon's  theory  concerns  de- 
velopment. When  the  germ- cell  which  has  been  impressed 
with  '  engrams '  comes  to  develop,  a  partial  recurrence 
of  the  '  energetic  situation  ',  which  previously  acted  '  en- 
graphically  ',  will  call  forth  the  latent  engrams  into  expres- 
sion. Given  appropriate  stimuli  the  '  memories  '  will  stir, 
and  they  will  influence  what  is  going  on,  namely  the 
development  of  the  individual. 

Let  us  recapitulate.  Year  after  year  a  complex  influ- 
ence plays  upon  the  organism  and  modifies  its  constitution. 
The  internal  '  energetic  situation '  is  changed  and  result- 
ing stimuli  are  supposed  to  pass  to  the  germ- cells.  The 
corresponding  changes  in  the  germ-cells  are  called  en- 


604  THE  WONDER  OF  LIFE 

grams.  When  the  germ  cells  come  to  develop  into 
offspring,  these  engrains  may  have  an  influence — a  specific 
influence.  Appropriate  liberating  stimuli  of  the  nature 
of  the  original  change  in  the  energetic  situation  will  call 
forth  the  latent  engrams.  This  is  called  '  ekphory '. 

In  support  of  his  nrnemic  theory  of  heredity  Semon 
cites,  among  other  facts,  Kammerer's  experiments  on  the 
Nurse-Toad  (Alytes  obstetricans}.  Unlike  ordinary  toads, 
the  female  lays  her  eggs  on  land,  and  the  male  who  assists 
in  the  process  gets  them  glued  on  his  hind  legs.  Moreover, 
the  eggs  are  larger  than  usual,  with  more  yolk,  and  fewer 
in  number. 

Kammerer  kept  the  toads  at  a  relatively  high  temperature 
(25°-30°  C.)  and  thus  induced  them  to  seek  the  water, 
where  the  egg-laying  and  fertilization  took  place.  The 
gelatinous  envelopes  of  the  eggs  which  had  remained  sticky 
and  unswollen  on  land,  now  swelled  up  as  usual,  and  as  they 
would  not  adhere  to  the  male's  legs,  the  eggs  developed 
in  the  water.  After  several  breeding  periods  the  toads 
became  accustomed  to  the  water ;  they  also  laid  more 
numerous  and  smaller  eggs. 

But  the  more  important  fact  is  this,  that  the  offspring 
of  the  toads  showed  a  change  of  habits  like  that  of  their 
parents.  When  they  became  sexually  mature  they  sought 
the  water,  even  when  kept  at  the  normal  temperature, 
and  laid  their  eggs  there.  The  fourth  generation  showed 
a  re- appearance  of  the  doubtless  ancestral  swollen  pad  on 
the  forefinger  of  the  male,  which  was  absent  in  the  race  of 
nurse-toads  with  which  Kammerer  experimented.  In 
Semon's  phrase  the  appropriate  stimuli  called  forth  the 
latent  ancestral  engrams. 

Provisional   Conclusion. — It  may  be   that   there  is 


THE  WONDER  OF  LIFE  605 

more  truth  in  the  Mnemic  interpretations  than  we  are 
personally  able  at  present  to  recognize,  and  we  have  no 
desire  to  be  dogmatic.  But  we  do  not  feel  that  the  evi- 
dence is  convincing. 

What  then  is  the  state  of  the  case?  The  individual 
profits  by  experience,  profits  in  his  protoplasm  and  cells, 
in  his  joints  and  marrow,  in  his  mind  and  character.  There 
is  no  secure  evidence,  however,  that  his  gains  are  in  any 
way  entailed,  or  that  his  losses  are  minuses  to  his  offspring. 
Yet  the  progress  of  a  race  or  stock  looks  as  if  these  profitable 
lessons  learnt  by  the  individual  did  somehow  count.  Now 
it  is  possible  that  the  germinal  primordia  of  various  char- 
acters, embodied  we  cannot  conceive  how  in  the  germ- cells, 
respond,  as  flames  to  tuning-forks,  to  the  lessons  which  the 
corresponding  actualized  characters  in  the  body  of  the 
individual  are  learning.  We  keep  an  open  mind  on  this 
question,  but  it  must  be  admitted  that  the  present-day 
facts  are  mainly,  though  not  exclusively,  against  this  view 
that  particular  modifications  of  the  parentage  do  specific- 
ally affect  the  progeny  in  the  same  direction.  If  this 
be  so,  what  then  remains  but  a  retreat  to  the  original  Dar- 
winian position  of  copious  germinal  variations — sufficiently 
copious  to  ensure  a  certain  number  of  (selectable)  hits 
amid  a  multitude  of  misses  ? 

The  question  ever  returns  :  What  is  trading  with  time 
good  for,  if  the  bodily  experiences  of  the  individual  do  not 
count  for  the  race  ?  For  that  is  what  it  comes  to.  We 
would  suggest  that  the  question  requires  some  re-setting. 
Our  biology  is  at  times  too  anthropomorphic  and  at  times 
not  anthropomorphic  enough.  In  human  affairs  we  con- 
tinually think  of  ourselves  as  experimenting,  trying  this 
and  trying  that,  and  finally  doing  something.  We  transfer 


606  THE   WONDER  OF  LIFE 

this  idea  to  the  non-rational  animals,  and  we  think  of 
them,  probably  aright,  as  trying  this  and  trying  that,  and 
finally  doing  something.  We  carry  this  idea  down  and 
down,  and  probably  it  is  much  truer  than  many  naturalists 
think,  but  we  doubt  whether  it  is  by  thinking  of  adult 
organisms  that  we  shall  understand  what  trading  with 
time  really  means. 

The  suggestion  we  wish  to  make  is  this.  No  one  will 
dispute  the  statement  that  an  Amoeba  may  profit  by  its 
experiences  and  may  make  experiments  '  in  the  light  of ' 
these  experiences.  Now  it  must  be  remembered  that  the 
germ- cells  or  gametes  are  not  ordinary  cells ;  they  are  indi- 
vidualities, organisms,  creatures,  who  live  and  multiply, 
who  struggle  and  combine,  who  are  repositories  of  multi- 
plicate  inheritances  adjusting  themselves  inter  se  in  the 
most  momentous  of  organic  compromises.  Now  it  may  be 
that  these  gametes — neither  simple  cells  nor  portmanteaus 
of  hereditary  items,  but  unified  '  creatures ',  experiment 
not  fortuitously,  but  artistically,  not  at  random,  but  with 
a  purpose. 

The  Living  Past. — In  any  case,  one  of  the  strongest 
impressions  that  we  get  from  the  study  of  organic  evolution 
is  that  of  the  persistence  of  the  past  in  the  present.  In  a 
manner  inconceivable  to  us,  save  through  the  analogy  of 
memory,  the  germ- cell  garners  the  long  results  of  time. 
To  some  extent  in  the  development  of  organs  in  the  indivi- 
dual there  is  a  recapitulation  of  stages  which  correspond 
to  long  chapters  in  the  evolution  of  the  race.  And  just 
as  we  recognize  traits  of  their  wild  lineage  in  our  domesti- 
cated animals,  so  in  a  wider  field  we  see  the  individual's 
organic  reminiscence  of  primeval  days  and  a  recrudescence 
of  ancestral  wounds.  In  ourselves  we  are  only  too  well 


THE  WONDER  OF  LIFE  607 

aware  of  these  '  palaeo- atavistic '  qualities.  There  is  a 
terrible  truth  in  Walt  Whitman's  picture  of  man  emerging 
'  stuccoed  all  over  with  reptiles  and  quadrupeds ',  and  in 
Tennyson's  picture  of  '  Reversion  ever  dragging  Evolution 
in  the  mud '.  As  Prof.  Stanley  Hall  says  : 

'  We  are  influenced  in  our  deeper,  more  temperamental, 
dispositions  by  the  life-habits  and  codes  of  conduct  of 
we  know  not  what  unnumbered  hosts  of  ancestors,  which 
like  a  cloud  of  witnesses  are  present  throughout  our  lives, 
and  our  souls  are  echo- chambers  in  which  their  whispers 
reverberate '. 

The  idea  of  the  living  past  is  familiar  in  connexion  with 
those  vestigial  structures,  like  the  teeth  in  whalebone 
whales,  which  persist  in  many  animals  as  tell-tale  evidences 
of  remote  ancestry — like  the  unsounded  letters  in  words 
or  the  superfluous  flaps  and  buttons  in  our  clothing  which 
once  had  a  functional  significance.  Our  own  body  is  a 
veritable  museum  of  relics — some  (like  the  notochord) 
disappearing  in  embryonic  life,  others  (like  the  Eustachian 
tube)  persisting  in  greatly  disguised  form,  others  (like  the 
third  eyelid)  remaining  as  dwindling  vestiges,  and  others 
(like  the  vermiform  appendix)  not  merely  outliving  their 
usefulness,  but  proving  themselves  dangerous  anachronisms. 

It  goes  without  saying  that  the  mere  persistence  of 
dwindling  organs  and  of  habits  that  have  become  anachron- 
isms, is  not  evidence  of  misadaptation.  The  useless  teeth 
of  the  baleen  whale,  the  unseeing  eyes  of  many  cave-animals, 
and  the  now  meaningless  relics  of  wild  habits  which  many 
domesticated  animals  exhibit,  present  no  particular  diffi- 
culty. They  are  the  vanishing  vestiges  of  characters 
that  were  once  effective  and  adaptive.  This  remains  a 
satisfactory  answer — except  to  those  who  expect  a  perfect 


6o8 


THE  WONDER  OF  LIFE 


cosmos — even  when  it  is  pointed  out  that  vestigial  organs 
are  often  very  variable  and  apt  to  be  seats  of  diseases 

(witness  appendicitis), 
and  that  anachronistic 
habits  form  part  of 
what  men  call  crimes. 
None  but  the  un- 
imaginative can  fail  to 
be  impressed  by  the 
sight  of  the  pelvic 
bones  of  a  large  whale. 
Dwindling  relics  they 
are  of  originally  huge 
hip-girdles.  They  may 
be  connected  with  ad- 
jacent muscles — a  tail 
muscle,  the  genital 
muscles,  and  a  trunk 
muscle,  but  they  are 
practically  of  no  mo- 
ment. Eontgen  ray 
photographs  show  that 
they  still  retain,  how- 

FIG.  93.-Vestigialhip-girdleandhind.limb   6Ver> the  Characteristic 
of  a  whale.    1,  Vestige  of  pelvis  or  internal  architecture  of 

hip-girdle;  2,  Vestige  of  thigh-bone  or  ,  Q         ,. 

femur  ;  3,  Cartilage  corresponding  to  bone-      bometimeS,     as 

the   tibia.     The  closely  dotted  parts  tne  fig^e  g^ows,  there 

are  cartilage.     I  he  dotted  line  crossing  J     . 

2  shows  the  contour  of  the  pelvis  ;  are   vestiges    not   Only 

M,  muscles  attached  to  these  pieces  of      e    .1        ™»hn« 

skeleton.     (After  Struthers.)  ot    tne    PelV1S 


only  by  the  ischiac  portion),  but    of    femur   and   tibia 
as  well.    Careful  measurement  made   by  Willy  Augustin. 


THE  WONDER  OF  LIFE  609 

of  the  pelvic  vestiges  of  the  Finner  (Balcenoptera  physalus), 
the  Blue  Whale  (B.  sibbaldi),  Rudolphi's  Rorqual  (B. 
borealis)  and  the  Humpback  (Megaptera  boops)  show 
that  the  bones,  like  many  vestigial  structures,  are  in  a  state 
of  considerable  variability. 

We  have  given  two  figures  of  a  very  interesting  and 
puzzling  structure  connected  with  the  roof  of  the  brain 
in  Vertebrates.  From  the  region  known  as  the  'tween-brain 
or  optic  thalami  there  is  a  dorsal  up-growth,  usually  con- 


FIG.  94. — Vertical  section  showing  the  pineal  eye  of  the  adult  slow- 
worm,  Anguis  fragilis.  (After  Hanitsch.)  1 ,  Cuticle  ;  2,  Epidermis  ; 
3,  Connective  tissue  ;  4,  Parietal  bone  of  the  skull ;  [5,  Lens  of  pineal 
eye ;  6,  Wall  of  pineal  eye  ;  7,  Epiphysis  or  upgrowth  from  the 
brain.  It  is  here  continuous  with  the  stalk  of  the  pineal  eye. 
According  to  Hanitsch,  the  pineal  eye  in  the  slowiworm  is 
sensitive  to  changes  of  temperature. 


sisting  of  two  parts,  a  pineal  organ  or  epiphysis  proper, 
and  a  parietal  organ,  which  generally  springs  from  the 
epiphysis,  but  may  have  an  independent  origin  in  front  of 
it.  Perhaps  they  were  originally  the  right  and  left  mem- 
bers of  a  pair.  The  parietal  organ  is  often  atrophied, 
but  in  some  cases,  especially  in  Reptiles,  it  is  terminally 
differentiated  into  a  little  '  pineal  body.'  In  the  New 
Zealand  '  lizard '  (Sphenodon)  and  in  the  slow- worm 
(Anguis)  it  shows  distinct  traces  of  eye-like  structure. 

R  R 


6io  THE  WONDER  OF  LIFE 

In  the  lamprey,  both  the  epiphysis  and  the  parietal  organ 
show  this.  Above  Reptiles  the  pineal  stalk  is  short  and 
its  terminal  portion  is  glandular.  The  epiphysis  is  occa- 
sionally absent  in  Mammals  (e.g.  some  Cetaceans),  and 
the  pineal  body  is  absent  in  the  dolphin  and  Dasypus. 
According  to  some  authorities,  the  pineal  body  was  primi- 
tively an  unpaired  median,  upward-looking  eye  ;  according 
to  others,  the  optic  function  is  a  secondary  transformation. 

,3 


FIG.  95.— Section  showing  developing  pineal  eye  of  Sphenodon.  (After 
Dendy.)  1,  Epidermis;  2,  Dermis  ;  3,  Lens;  4,  Wall  of  pineal 
eye  ;  5,  Choroid  plexus  of  dorsal  sac,  on  the  roof  of  the  third  ven- 
tricle of  the  brain  ;  6,  Nerve  of  pineal  eye  ;  7,  Pineal  sac. 

For  it  not  infrequently  happens  that  a  dwindling  structure, 
tending  to  become  vestigial,  may  become  secondarily 
specialized.  Thus  the  vestigial  hairs  on  the  lips  of  some 
whales  have  a  quite  extraordinarily  rich  innervation. 
It  must  be  frankly  admitted  that  many  of  the  examples 
that  used  to  be  given  of  the  re-assertion  of  long-lost  an- 
cestral characters  were  insufficiently  criticized,  and  the 
list  of  so-called  reversions  has  been  remorselessly  thinned 
by  the  more  modern  students  of  inheritance.  Sometimes, 


THE  WONDER  OF  LIFE  611 

however,  it  does  seem  as  if  the  return  to  an  old-fashioned 
condition  was  best  explained  by  the  hypothesis  of  the 
re-awakening  of  an  ancestral  trait  which  had  lain  latent 
for  many  generations. 

In  other  cases  it  seems  more  likely  that  some  derange- 
ment of  development  has  resulted  in  a  suggestion  of  an  an- 
cient condition  without  there  being  any  re- awakening  of 
any  particular  ancestral  item  in  the  inheritance.  Probably 
this  is  the  case  with  most  of  the  two- toed  horses  that  crop 
up.  But  some  of  them  are  strongly  suggestive  of  more 
than  this.  Thus  Prof.  K.  Skoda,  of  the  Veterinary  College 
in  Vienna,  describes  a  case  where  each  fore-leg  bore  beside 
the  normal  single  digit  (No.  Ill)  a  second.  This  second 
(No.  II)  had  three  joints,  but  did  not  reach  the  ground. 
There  was  a  metacarpal  (or  palm-bone)  for  this  extra 
digit,  but  it  was  largely  fused  with  the  ordinary  meta- 
carpal of  No.  III.  The  usual  No.  IV.  free  splint  or  meta- 
carpal was  present,  and  there  seemed  to  be  actually  hints 
of  a  minute  metacarpal  No.  I.  Especially  when  we  look 
into  the  details  of  a  case  like  this  does  it  seem  difficult  to 
dissociate  what  occurred  from  all  relation  to  the  ancient 
polydactyl. 

To  some  minds  it  seems  very  inconsistent  to  credit  the 
germ-plasm  at  one  time  with  great  stability,  and  at  another 
time  with  great  power  of  change.  But  there  is  really  no 
paradox  here,  for  every  thinker  with  a  lively  intelligence 
shows  the  same  combination  of  qu.'-ilities — holding  by 
fundamental  principles,  yet  restlessly  experimenting  with  an 
open  mind.  So  the  germ- plasm  in  its  own  fashion  proves  all 
things  and  holds  fast  that  which  is  good.  Moreover,  it  is 
quite  likely  that  the  varying  or  mutatir\g  occurs  periodically. 
Just  as  we  have  an  alternation  between  speculation  and 


612  THE  WONDER  OF  LIFE 

dogmatism,  between  liberal  and  conservative  moods,  so 
the  germ-plasm  may  have  what  correspond  to  originative 
and  fixative  moods. 

As  an  instance  of  the  stability  of  the  germ-plasm,  even 
when  violently  treated,  we  may  take  Dr.  D.  D.  Whitney's 
investigation  of  the  effect  of  alcohol  on  generations  of 
Rotifers.  He  studied  four  strains  of  parthenogenetic 
Rotifers,  originally  descended  from  one  female,  for  twenty- 
eight  successive  generations.  One  strain  was  kept  as  a 
control,  and  the  other  three  strains  were  kept  in  a  quarter 
per  cent.,  a  half  per  cent.,  and  one  per  cent,  of  alcohol.  The 
rate  of  reproduction  was  lessened  in  the  alcoholic  strains 
and  the  resistance  power  was  lowered.  In  the  eleventh  to 
fifteenth  generations  of  the  one  per  cent,  alcohol  strain,  the 
individuals  showed  a  decidedly  lower  resistance  power.  They 
exhibited  a  markedly  increased  susceptibility  to  copper 
sulphate  which  was  used  as  a  test  of  resistance.  The  result 
showed,  then,  the  evil  effects  of  alcohol.  But  whether  it 
showed  the  hereditary  evil  effects  or  not  remained  to  be 
seen. 

When  the  alcohol  was  removed  in  generations  eleven  to 
twenty-two,  the  rate  of  reproduction  increased  noticeably  in 
the  very  first  generation,  and  in  the  second  equalled  that 
of  the  control  strain.  Individuals  of  the  second  generation 
after  the  alcohol  had  been  removed  were  no  more  susceptible 
to  copper  sulphate  than  those  which  had  never  been  alco- 
holized. The  general  conclusion  is  that  the  grandchildren 
possess  none  of  the  defects  caused  by  alcohol  in  the  grand- 
parents. The  alcohol,  in  the  small  percentages  used, 
affected  only  the  body-tissues  of  the  Rotifers,  which  is  not, 
of  course,  to  be  interpreted  as  meaning  that  chronic  alcohol- 
ism in  man  may  not  affect  the  germ- cells.  Dr.  Whitney 


THE  WONDER  OF  LIFE  613 

also  points  out  that  if  the  Rotifers  were  subjected  to  the 
alcohol  solution  indefinitely,  generation  after  generation,  the 
race  would  probably  become  extinct.  The  alcohol  lessens 
the  rate  of  reproduction  and  it  may,  in  the  course  of  time, 
progressively  weaken  the  germ-cells.  What  was  proved, 
however,  was  that  '  if  the  alcohol  is  removed  it  is  possible 
for  the  race  to  recover  and  to  regain  its  normal  condition 
in  two  generations,  thus  showing  that  the  germ- substance 
is  not  permanently  affected  by  the  alcohol '  so  far  as  the 
experiments  went.  In  any  case  we  have  a  good  instance 
of  the  stability  of  the  germ- plasm. 

It  is  only  fair,  however,  to  cite  a  case  on  the  other  side, 
indicating  susceptibility.  Dr.  Charles  R.  Stockard  made 
experiments  for  three  years  in  intoxicating  male  guinea- 
pigs  by  inhalation  of  alcohol  (which  does  not  spoil  their 
stomach),  and  reached  the  important  conclusion  that  an 
alcoholized  male  guinea-pig  almost  invariably  begets 
defective  offspring  even  when  mated  with  a  vigorous 
normal  female.  The  effects  were  manifest  in  the  second 
generation  animals  as  well.  '  The  poison  injures  the  cells 
and  tissues  of  the  body,  the  germ-cells  as  well  as  other 
cells,  and  the  offspring  derived  from  the  weakened  or 
affected  germ- cells  have  all  of  the  cells  of  their  bodies 
defective.' 

Dentition  of  Shrews. — Let  us  take  a  somewhat  un- 
familiar illustration  of  a  persistent  relic.  It  is  well  known 
that  in  ordinary  placental  mammals  with  various  kinds 
of  teeth  (heterodont  as  it  is  called),  there  are  never 
more  than  three  pairs  of  incisors.  There  is  thus  a  gap 
between  all  ordinary  mammals  and  the  old-fashioned 
Polyprotodont  Marsupials,  such  as  the  Tasmanian  Wolf 
or  Thylacine,  which  has  four  upper  incisors,  and  the  Bandi- 


614  THE  WONDER  OF  LIFE 

coot  (Perameles)  which  has  five.  Now  a  study  of  the 
development  of  the  teeth  in  shrews  led  Augusta  Arnback- 
Christie-Linde  to  the  very  interesting  discovery,  that 
there  are  more  than  three  incisor  germs  in  both  jaws  of 
Sorex  araneus,  and  probably  also  in  the  upper  jaw  of 
Neomys.  These  extra  incisor  germs  in  the  Shrew  are 
apparently  useless  relics — vestigial  structures  without 
any  function.  They  come  and  they  go  without  attaining 
full  development.  '  They  are ',  the  discoverer  says, 
'  undoubtedly  inherited  from  distant  ancestors,  which 
consequently  were  to  be  found  among  polyprotodont  (and 
heterodont)  mammals '.  As  regards  the  number  of 
incisor  teeth  it  seems  as  if  the  Shrews  bridged  the  gap  to 
which  we  alluded  above.  In  any  case,  these  extra  incisor 
germs  seem  to  illustrate  our  present  point — of  the  long 
lingering  of  structural  relics  which  have  outlived  their  use. 

In  the  inner  upper  corner  of  our  eye  there  is  a  minute 
half -moon- shaped  fold,  the  plica  semilunaris,  a  most 
interesting  item  in  the  museum  of  relics  which  we  carry 
about  with  us  in  our  body.  For  it  corresponds  to  the 
third  eyelid  (in  whole  or  in  part)  which  is  well- developed 
in  most  mammals  and  helps  to  clean  the  eye.  It  is  vestigial 
not  only  in  Man,  but  in  Monkeys  and  in  Cetaceans.  Its 
practical  absence  in  the  Cetaceans  is  compensated  for  by 
the  continuous  washing  of  the  eye  with  water.  In  the 
other  cases  the  frequent  movements  of  the  upper  eyelid 
must  make  up  for  the  vestigial  state  of  the  third  eyelid.  It 
is  a  very  old  structure,  a  venerable  relic,  for  it  is  the  '  nicti- 
tating membrane '  that  is  flicked  across  the  eyes  of  Birds 
and  it  is  also  represented  in  most  Reptiles. 

It  may  be  profitable  to  pursue  the  matter  a  little  further. 
The  plica  semilunaris  sometimes  includes  in  man  a  minute 


THE  WONDER  OF  LIFE  615 

cartilage — a  tell-tale  cartilage.  In  white  races  it  is  a  great 
rarity,  occurring  in  less  than  one  per  cent.  Giacomini 
found  it  in  four  cases  out  of  five  hundred  and  forty- eight 
whites.  But  he  found  it  twelve  times  in  sixteen  coloured 
people,  and  Adachi  found  it  five  times  in  twenty-five 
Japanese.  More  recently  Dr.  Paul  Bartels  examined  twenty- 
five  South  African  natives  (eight  Hereros  and  seventeen 
Hottentots)  and  found  the  tell-tale  cartilage  in  twelve. 
The  cartilage  is  found  in  all  Apes  and  Monkeys,  and  although 
no  living  Ape  or  Monkey  is  ancestral  to  Man,  the  cartilage 
is  a  Simian  feature,  persisting  in  Man  since  the  remote 
period  when  the  human  stock  diverged  from  the  Simian. 
The  facts  show  that  some  races  are  in  this  instance  as  in 
others,  more  theromorphic  than  others — more  conser- 
vative of  their  historical  relics. 

One  has,  of  course,  to  be  careful  in  using  this  interpre- 
tation of  peculiarities  as  atavisms.  It  is  probable  that  in 
some  cases  all  that  we  are  justified  in  saying  is  that  a  varia- 
tion occurs  which  happens  to  be  along  very  antique  lines. 
To  take  an  example,  the  teeth  of  mammals  begin  as  in- 
growths of  the  (ectodermic)  epithelium  into  the  (meso- 
dermic)  connective  tissue  of  the  gum,  whereas  the  teeth 
of  sharks  and  skates  and  other  Selachian  fishes  begin  as 
papillae  of  the  mesoderm  which  grow  up  into  the  epidermis. 
The  teeth  of  Selachians  are  just  transformed  scales,  turned 
to  a  new  use.  But  it  is  a  remarkable  fact  that  the  Sela- 
chian or  placoid  mode  of  tooth  development  does  occur 
in  Bony  Fishes,  tailed  Amphibians,  and  in  the  crocodile. 
Rose  has  seen  hints  of  it  in  the  human  embryo,  and  not 
long  ago  (1911)  Adloff  found  in  a  human  embryo,  of  about 
nine  weeks,  a  freely  projecting  epithelial  papilla  lying 
beside  a  normal  tooth-germ.  He  regarded  it  as  an  atavistic 


616  THE  WONDER  OF  LIFE 

rehabilitation  of  the  oldest  mode  of  tooth- development. 

Amphibian  Scales. — Sometimes  it  seems  quite  legiti- 
mate to  recognize  a  structure  as  a  relic  although  we  are 
not  aware  of  the  precise  affiliation.  Every  one  knows 
that  almost  all  amphibians  are  naked-skinned  or  scaleless 
in  great  contrast  to  the  scaly  Reptiles.  It  is  also  well 
known  that  some  of  the  ancient  extinct  Amphibians,  the 
Labyrinthodonts  or  Stegocephali,  were  armoured.  There- 
fore it  is  interesting  to  find  in  the  most  old-fashioned  stocks 
of  living  Amphibians,  namely  the  burrowing  Csecilians, 
that  there  are  transverse  rows  of  thin  calcined  scales 
imbedded  in  the  dermis  or  under-skin.  Moreover,  in  a  few 
rare  cases  among  tailless  Amphibians,  there  are  bony  scales 
in  the  skin.  Thus  in  Ceratophrys  dorsata  there  is  a  bony 
shield  on  the  back  which  arises  from  the  confluence  of  a 
large  number  of  small  ossifications  in  the  dermis.  It  is 
very  unlikely  that  this  can  mean  anything  but  a  retention 
of  the  ancestral  armour.  Not  less  interesting,  though  less 
secure,  is  Margarethe  Kressmann's  interpretation  of 
numerous  papillae  that  occur  all  over  the  lower  layer  of 
the  dermis  in  Siren  lacertina,  the  American  mud- eel. 
Each  consists  of  firm  connective  tissue  and  is  usually  tipped 
with  a  mantle  of  pigment.  They  project  into  the  more 
superficial  looser  layer  of  the  dermis  and  are  quite  hidden 
from  the  outside.  It  seems  reasonable  to  interpret  them 
as  dwindling  vestiges  of  the  ancestral  armature. 

The  Egg  Tooth.— At  the  tip  of  the  bill  of  many  un- 
hatched  young  birds  there  is  a  horny  knob  which  is  called 
the  egg- tooth.  It  has  nothing  whatever  to  do  with  teeth, 
of  which,  as  separate  structures,  no  living  bird  is  known 
to  show  any  hint  (the  alleged  cases  of  tern,  etc.,  having 
broken  down) ;  but  it  is  interesting  in  several  ways.  If  it 


THE  WONDER  OF  LIFE  617 

is  of  use  in  breaking  through  the  egg-shell  to  liberate  the 
young  bird,  which  seems,  in  some  cases  at  least,  to  be 
very  doubtful,  then  it  is  one  of  those  structures  which  are 
used  only  once.  As  every  one  knows,  it  usually  falls  off 
soon  after  hatching. 

This  fact  suggests  that  it  may  not  be  a  special  structure 
that  has  evolved  on  a  line  of  its  own,  but  the  last  relic  of 
an  old  set  of  structures,  retained  because  of  its  utility 
while  all  the  others  have  gone.  Some  recent  observations 
by  B.  Rosenstadt  suggest  that  the  egg-tooth  of  the  upper 
jaw  and  its  corresponding  vestige  on  the  lower  jaw,  maybe  ••£ 
relics  of  an  ancient  armature,  older  than  the  horny  sheaths 
we  are  familiar  with  on  the  bird's  jaws.  In  the  first  place 
they  become  horny  in  the  embryo  before  there  is  any  other 
cornification  on  the  jaws.  In  the  second  place,  the  process 
of  horn-making  in  the  egg  tooth  is  different  from  that 
elsewhere.  Each  of  the  skin  cells  concerned  turns  wholly 
into  horn,  nucleus  and  all,  whereas  in  ordinary  cases,  as 
in  the  horny  sheaths  that  make  the  bill,  only  the  mantle 
of  each  cell  is  turned  into  horn.  This  is  a  technical  point, 
but  it  is  of  interest  in  suggesting  that  the  egg-tooth  is  a  £,>• 
very  ancient  relic  indeed. 

Whales'  Hairs. — Let  us  look  at  the  fact  of  whales' 
hairs.  If  we  could  understand  these,  we  should  have  a 
master-key  in  our  hand.  The  points  are  three.  (1)  The 
ancestry  of  Cetaceans  is  unknown,  but  they  are  quadrupeds 
and  mammals  none  the  less  that  the  remains  of  the  hind- 
limbs  are  buried,  and  that  their  hairs  are  reduced  to  a 
minimum.  It  is  possible  that  whales  were  evolved  from 
scale- covered  Mammals,  which  took  to  aquatic  life.  The 
slight  resemblance  of  the  whale's  flipper  to  that  of  the 
extinct  Ichthyosaurian  reptiles  cannot  mean  much;  for 


618  THE  WONDER  OF  LIFE 

the  flipper-type  must  have  arisen  de  novo  in  the  Cetaceans. 
It  is  a  specialized  transformation  of  a  typical  mammalian 
limb,  just  as  the  skull  is  a  specialization  of  a  typical  mam- 
malian skull. 

(2)  Although  the  divergence  of  Cetaceans  from  a  terres- 
trial stock  must  have  taken  place  very  long  ago,  the  loss 
of  hair  may  have  been  very  gradual,  or  it  may  have  occurred 
brusquely,  by  a  mutation  such  as  we  see  in  '  Chinese  dogs  '. 
It  is  a  remarkable  fact  that  they  seem  never  to  disappear 
altogether.     Although  the  inexperienced  eye  may  see  none, 
there  is  probably  no  species  entirely  without  them.     Dr. 
Arnold  Japhen  recently  examined  five  kinds  of  baleen 
whales  and  six  kinds  of  toothed  whales,  and  found  hairs 
about  the  lips  of  them  all.     Therefore  we  must  admit  that 
the  capacity  of  forming  hairs  remains  still  in  the  Cetacean 
skin,  that,  in  some  way  or  other,  the  potentiality  of  hairs 
persists  as  a  dwindling  relic  as  part  of  the  inheritance.     It 
is  very  interesting  to  find  that  apart  from  their  great  reduc- 
tion in  number,  the  hairs  show  distinct  signs  of  retrogression. 
The    hair-muscles  and  the  sebaceous  glands  have  gone, 
the  hair  shaft  is  greatly  reduced,  what  is  called  the  root- 
sheath  is  simpler  than  usual,  and  there  is  no  hair  casting. 

(3)  On  the  other  hand,  we  find  in  regard  to  whales' 
hair  an  illustration  of  what  has  often  occurred  in  the 
course   of  evolution — that  vestigial    structures  may    be 
utilized,  indeed  specialized,  even    when    they    are    very 
much   reduced.     It   seems,    metaphorically   speaking,    as 
if  the  organism  sometimes  saved  its  historical  relics  just 
as  they  were  disappearing  by  discovering  some  utilitarian 
vindication  of  them.     For  these  small  retrogressed  hairs 
on  the  whales'  lips  exhibit  at  the  same  time  a  remarkable 
specialization,  namely  in  their  rich  supply  of  nerve-fibres 


THE  WONDER  OF  LIFE 


619 


and  in  the  way  these  end  in  the  hair-follicle.  There  may 
be  four  hundred  nerve-fibres  to  a  single  hair,  so  that  if 
there  are  twenty-five  hairs  on  the  chin  region,  there  are 


FIG.  96. — King  Crab,  Limulus,  seen  from  above.  It  is  an  archaic 
type,  a  veritable  '  living  fossil,'  the  sole  survivor'  of  the  ancient 
race  of  Palaeostraca.  The  figure  shows  the  horseshoe-shaped 
cephalothorax  shield,  bearing  lateral  and  median  eyes  ;  the  ab- 
dominal shield  ;  and  a  spear  or  telson  projecting  behind.  (From 
a  specimen.) 

ten  thousand  nerve  fibres.  The  vestigial  hairs  seem  like 
specializations  of  the  tactile  hairs  or  vibrissse  which  every 
one  knows  in  a  cat's  whiskers.  In  the  toothless  Cetaceans 


620 


THE  WONDER  OF  LIFE 


at  least,  it  seems  highly  probable  that  these  richly  inner- 
vated, though  much  reduced  structures,  play  some  role 
in  connexion  with  food-getting. 
Living  Fossils. — Of  great  in- 
terest in  this  connexion  are  those 
old-world  types  such  as  Peripatus 
and  Limulus,  Polypterus  and  the 
Dipnoi,  Sphenodon  and  the  Mono- 
tremes — survivors  of  ancient  races. 
One  of  these  living  fossils  is 
the  hoatzin  (Opisthocomus),  an 
extremely  ancient  and  isolated 
type,  frequenting  the  lower 
Amazon  and  surrounding  terri- 
tory. One  of  its  primitive 
features  is  the  quadrupedal 
character  of  the  young,  which 
use  their  fore-limbs  for  creeping 
about  with  on  the  branches. 
They  also  dive  and  swim  well. 
There  are  external  claws  on  the 
first  and  second  fingers  and  a 
vestigial  claw  on  the  third.  The 
hand- like  use  of  the  wing  is 
present  in  the  adults  as  well,  who 
never  fly  if  they  can  help  it.  Mr. 
Beebe  notes  that  '  their  method 
of  arboreal  locomotion  is  to  push 
and  flop  from  branch  to  branch  '. 
Their  weakness  of  flight  is  doubt- 
less in  part  due  to  a  curious 
specialization,  that  the  crop  has 


«i 


FIG.  97.  —  Peripatus,  an 
ancient  type,  in  some  re- 
spects linking  segmented 
worms  to  Insects.  The 
figure  shows  antennae, 
simple  eyes,  simple 
clawed  appendages,  and 
an  unsegmented  some- 
what cater  pillar-like 
body.  (After  Balfour.) 


THE   WONDER  OF  LIFE  621 

become  like  a  gizzard,  with  thick  and  muscular  walls. 
This  is  associated  with  a  unique  reduction  of  the  front 
of  the  breast-bone,  and  a  consequent  lessening  of  the 
area  for  the  attachment  of  the  muscles  of  flight. 


FIG.  98. — New  Zealand  Lizard,  Sphenodon  or  Hatteria,  an  archaic 
reptilian  type,  sole  survivor  of  the  ancient  race  of  Rhynchocephalia. 
(From  a  specimen.) 

Conservation  in  Evolution. — We  wish  to  expand  the 
idea  of  the  living  past  into  a  general  conception  of  the 
conservative  tendency  in  evolution.  There  is,  it  seems  to 
us,  a  very  literal  sense  in  which  we  may  think  of  the  higher 
animals  as  heirs  of  all  the  ages.  Particularly  effective 
modes  of  vital  behaviour,  some  of  which  made  a  fortune 
in  their  day,  yet  did  not  save  their  possessors  from  utter 
ruin,  have  been  caught  up  by  collateral  relatives  and 
handed  on  as  a  legacy  from  by-gone  ages  to  the  higher 
animals.  Where,  for  instance,  would  a  higher  animal 
be — what  possibility  of  such  a  life  would  there  be — without 
a  persistence  of  that  most  primitive  manifestation  of  life 
which  we  call  amoeboid  movement — the  ebb  and  flow 
of  a  protoplasmic  tide — so  familiar  to  students  of  biology 
in  amoebae  and  white  blood  corpuscles  ?  How  long  would 
a  higher  animal  survive  without  its  body-guard  of  phago- 
cytes ?  Nor  could  it  have  become  what  it  is,  had  not  its 
embryonic  nerve-cells  flowed  out  into  nerve- fibres;  just  like 
exploring  Amoebae  ! 


622  THE  WONDER  OF  LIFE 

One  of  Harrison's  devices  was  to  excise  a  small  portion 
of  nerve  cord  from  an  embryo  frog,  and  to  replace  this  by  a 
cylindrical  clot  of  blood  or  lymph  of  the  proper  length  and 
calibre.  After  two  or  three  days  the  embryo  was  killed 
and  sectioned.  It  was  found  that  fibres  from  the  brain 
and  anterior  part  of  the  cord  had  grown,  or  flowed,  for  a 
considerable  distance  into  the  cord,  forming  naked  threads. 
But  the  general  point  with  which  we  are  here  concerned 
is  that  the  development  of  nerve-fibres  is  brought  about 
by  one  of  the  very  primitive  properties  of  protoplasm, 
namely  amoeboid  movement. 

It  is  very  interesting  that  the  only  animal  types 
without  wandering  phagocytes  are  the  Nematodes 
(some  of  which  at  least  have  stationary  phagocytes)  and 
the  Lancelets.  The  Nematode  worms  do  not  lead  on 
to  anything  else ;  and  the  Lancelets,  though  near  the 
base  of  the  Vertebrate  branch,  are  specialized  types 
on  a  cul-de-sac  of  their  own  !  It  appears  to  us  profoundly 
significant  that  Man  himself  in  the  development  of  his 
nervous  system,  in  the  repair  of  an  injury  to  the  front  of 
his  eye,  in  the  everyday  resistance  to  intruding  Bacteria, 
and  in  every  inflammation,  serious  or  trivial,  harks  back 
in  his  cellular  activities  to  the  Amoebae  gliding  along  on  the 
mud  of  the  pond. 

VITALISM 

The  Purely  Physical. — Among  the  facts  with  which  the 
student  of  science  has  to  deal  there  are  many  which  he 
calls  purely  physical — the  movements  of  the  earth  and  the 
heavenly  bodies,  the  seasons  and  tides,  the  sun  and  the 
wind  and  the  rain,  the  weathering  of  the  mountains,  the 
making  of  the  fruitful  land,  and  so  forth.  The  reality 


THE  WONDER  OF  LIFE  623 

which  these  facts  represent  may  not  be  exhausted  by 
formulae  in  terms  of  matter  and  motion,  but  for  the  theore- 
tical purposes  of  description,  and  for  the  practical  purposes 
of  anticipation  and  mastery  these  formulae  suffice.  The 
facts  may  be  treated  as  parts  of  a  mechanism,  on  the  view 
that  all  are  '  merely  complicated  cases  of  change  of  con- 
figuration in  a  system  of  mass  particles  '.  The  processes  of 
the  physical  order  are  marked,  as  every  one  knows,  by  their 
rigid  uniformity  of  routine,  their  monotonous  sequences, 
which  are  like  chains  of  iron.  They  can  be  described  with 
extraordinary  precision — on  which  we  stake  our  lives 
every  day — by  means  of  formulae  which  have  only  a  few 
factors  in  them.  At  present,  these  factors  seem  to  be  not 
more  than  five — the  ether,  the  electron,  the  atom,  the 
molecule,  and  the  mass,  energy  being  '  involved  in  the 
construction  of  any  of  these  out  of  any  other '.  The 
question  with  which  vitalists  are  chiefly  concerned  is 
whether  these  concepts  are  adequate  for  a  useful  descrip- 
tion of  the  activities  of  organisms — for  a  description  which 
will  make  the  facts  of  life  more  intelligible,  by  showing 
them  to  be  particular  cases  of  something  more  general. 
For  that  is  what  '  making  a  thing  intelligible  '  usually 
means.  It  must  be  quite  clearly  understood  that  as 
material  systems  in  space,  organisms  '  conform  to  the  laws 
of  the  physical  universe '  :  gravity  affects  a  bird  just  as 
it  affects  a  stone,  the  properties  of  a  hydrogen  atom  are 
the  same  whether  it  forms  part  of  a  scholar  or  of  his  mid- 
night oil,  capillarity  is  as  inexorable  in  a  blood  vessel  as  in 
a  glass  tube ;  but  what  the  vitalist  says  is  that  all  the 
available  knowledge  of  chemical  and  physical  happenings 
within  the  organism  does  not  begin  to  answer  the  distinc- 
tively biological  questions. 


624  THE  WONDER  OF  LIFE 

The  Animate. — That  the  animate  order  of  facts  trans- 
cends in  some  way  the  purely  physical  seems  to  some  minds, 
and  to  certain  moods  of  other  minds,  almost  self-evident. 
The  world  of  life  is  full  of  individuality,  of  spontaneity,  and 
apparent  purposiveness.  Living  creatures  often  make 
fatal  mistakes  when  the  environment  is  too  much  for  them, 
but  in  their  normal  surroundings  what  is  characteristic 
is  their  effectiveness  of  response,  making  for  self-preserva- 
tion and  betterment.  They  are  genuine  agents,  trying,  or 
seeming  to  try,  one  reaction  after  another  until  they  find 
the  one  which  is  most  effective  ;  they  profit  by  experience. 

It  is  necessary,  however,  to  face  the  objection  that  these 
qualitative  criteria  of  livingness  are  manifest  only  in  the 
higher  reaches  of  the  animal  kingdom,  and  illustrate  the 
compounding  and  elaborating  that  goes  on  in  evolution. 
The  plant  seems  less  animate  than  the  animal,  the  coral  less 
animate  than  the  bird.  And  we  have  already  referred  to 
such  difficulties  as  are  presented  by  latent  life  and  local 
life,  by  the  survival  and  development  of  a  minute  fragment 
of  an  egg,  and  by  the  fertilization  of  a  frog's  egg  by  a  pin's 
prick.  We  must  not  take  selected  instances  of  life's  apart- 
ness ;  we  must  consider  vital  phenomena  all  along  the  line. 

Argument  from  everyday  Functions. — When  we 
take  counsel  with  the  physiologists  and  inquire  into  the 
contraction  of  muscles,  the  irritation  of  nerves,  the  diges- 
tion and  absorption  of  food,  the  process  of  respiration,  and 
the  filtering  of  blood  by  the  kidneys,  we  find  that  many 
chemical  and  physical  processes  are  involved,  but  that  it 
has  not  yet  been  found  possible  to  give  a  continuous 
physico-chemical  description  of  any  total  vital  function. 
We  can  isolate  off  portions  of  a  function  and  watch  them 
occurring  in  a  test-tube  away  from  the  living  body  alto- 


THE  WONDER  OF  LIFE  625 

gether,  but  we  cannot  re-combine  our  analyses  so  as  to 
account  for  the  whole. 

It  is  not  merely  what  happens,  but  the  way  in  which  it 
happens,  that  we  have  to  consider.  If  we  inquire  into  the 
passage  of  digested  food  from  the  alimentary  canal  into  the 
blood,  or  the  interchange  of  gases  in  the  lungs,  or  the  filter- 
ing that  goes  on  in  the  kidney,  we  certainly  find  that 
these  involve  physico-chemical  processes,  and  we  detect 
in  their  occurrence  nothing  that  contradicts  the  principles 
of  physics  and  chemistry ;  and  yet  the  physico-chemical 
formulae  do  not  suffice  for  a  complete  description  of  the 
vital  function.  They  do  not  quite  fit ;  the  living  cells 
make  a  difference — a  difference  which  we  have  at  present 
to  accept  as  a  fact. 

Every  year  we  know  more  about  the  physical  and 
chemical  processes  that  occur  in  living  bodies,  but  it  does 
not  seem  as  if  the  physico-chemical  explanation  of  vital 
functions  was  coming  any  nearer.  We  do  not  know  what 
the  future  may  have  in  store  ;  but  we  must  take  things 
as  they  are,  and  there  is  surely  significance  in  the  fact 
that  increased  knowledge  of  physiological  chemistry  and 
physiological  physics  has  brought  the  distinctively  vital 
into  stronger  relief.  It  has  not  made  the  distinctively 
vital  more  intelligible ;  that  is,  it  has  not  shown  it  to  be  a 
particular  instance  of  something  more  general. 

Treating  the  organism  as  a  machine  has  led  to  great 
clearness  in  regard  to  the  big  transformations  of  energy 
that  go  on  in  the  body.  Without  Chemistry  and  Physics 
applied  to  the  living  body,  what  would  be  our  understand- 
ing of  respiration,  of  animal  heat,  of  muscular  work,  or  of 
the  significance  of  the  various  kinds  of  waste  ?  And  yet 
what  works  well  as  an  engine  of  research,  does  not  suffice 

S  8 


626  THE  WONDER  OF  LIFE 

for  a  formulation  of  the  facts — of  the  way  in  which  the 
great  workshop  of  the  body  is  regulated,  of  the  way  in 
which  the  different  functions  are  adjusted  to  every  varying 
need,  of  the  way  in  which  they  work  into  one  another's 
hands,  so  that  a  unified  effective  life  results.  To  take  one 
instance,  it  is  no  longer  a  difficult  physico-chemical  problem 
to  account  for  the  '  animal  heat '  of  the  living  body  (or 
for  a  large  fraction  of  it,  at  any  rate),  but  this  does  not 
help  us  much  to  account  for  '  warm-bloodedness  ' ;  that  is 
to  say,  for  the  regulation  of  heat-production  and  heat-loss, 
so  that  the  temperature  of  the  body  of  the  bird  or  the 
mammal  remains  approximately  constant  whatever  the 
outside  temperature  may  be.  Much  is  known  in  regard 
to  the  so-called  '  thermotaxic  mechanism  ',  but  the  more  we 
know  the  further  off  it  seems  from  mechanical  explanation. 

If  no  everyday  function  of  the  body  has  found  complete 
re- description  in  physico-chemical  terms,  it  follows  a 
fortiori  that  we  are  not  within  sight  of  an  explanation  of 
such  fundamental  vital  processes  as  growth  and  repro- 
duction. As  we  have  already  seen,  organic  growth  is  no 
process  of  passive  accretion,  it  is  selective  and  integrative. 
The  new  material  is  incorporated  and  unified ;  what  is 
added  on  is  related  essentially,  far  more  than  topographic- 
ally, to  what  is  already  present.  The  growth  is  a  repro- 
duction of  the  specific  organization  and  of  no  other. 

It  may  seem  strange  to  assert  that  even  if  we  had  a 
complete  record  of  all  the  transformations  of  matter  and 
energy  that  go  on  within  the  body  in  all  its  everyday 
functions,  we  should  not  be  answering  the  biological  ques- 
tions as  to  the  activity  of  the  creature  as  a  whole  :  What 
is  the  '  go  '  of  this  animal,  how  does  it  keep  agoing,  how 
do  the  various  functions  work  in  a  variable  way  into  one 


THE  WONDER  OF  LIFE  627 

another's  hands,  how  are  they  co-ordinated  in  a  harmoni- 
ous result,  how  are  they  adjustable  to  changeful  external 
conditions  ?  Even  a  complete  ledger  of  the  osmotic  and 
capillary  processes,  the  oxidations  and  reductions,  the 
solutions  and  fermentations,  would  not  furnish  the  kind  of 
description  the  biologist  wants. 

We  must  bear  in  mind  the  extraordinary  complexity 
of  the  problem  of  the  everyday  life  of  any  common  animal. 
For  what  is  a  creature  but  a  huge  army  with  battalions 
which  we  call  organs,  brigades  which  we  call  systems  ? 
It  advances  insurgently  from  day  to  day  always  into  new 
territory — often  inhospitable  or  actively  unfriendly ;  it 
holds  itself  together,  it  forages,  it  makes  good  its  own  losses, 
it  even  recruits  itself,  it  pitches  a  camp  and  strikes  it  again, 
it  goes  into  winter-quarters,  it  retreats,  it  recovers  itself, 
it  has  a  forced  march,  it  conquers.  What  the  biologist 
wishes  is  a  description  of  the  organism's  daily  march  which 
will  not  ignore  the  reality  of  the  tactics — the  intra-organis- 
mal  tactics. 

In  addressing  the  Physiological  Section  of  the  British 
Association  in  1909,  Professor  E.  H.  Starling  said : — 

'  In  his  study  of  living  beings  the  physiologist  has  one 
guiding  principle  which  plays  but  little  part  in  the  sciences 
of  the  chemist  and  physicist,  namely,  the  principle  of 
adaptation.  Adaptation  or  purposiveness  is  the  leading 
characteristic  of  every  one  of  the  functions  to  which  we 
devote  in^  our  textbooks  the  chapters  dealing  with  assimila- 
tion, respiration,  movement,  growth,  reproduction,  and 
even  death  itself '. 

Now  adaptation  or  purposiveness  requires  a  historical 
explanation  ;  it  is  a  supra-mechanical  concept.  It  is  true 


628  THE   WONDER  OF   LIFE 

that  it  applies,  in  a  measure,  to  a  machine,  but  a  machine 
is  the  embodiment  of  a  human  purpose.  It  is  an  elabor- 
ated tool,  an  extended  hand,  and  has  inside  of  it  a  human 
thought. 

The  Argument  from  Animal  Behaviour. — The 
inadequacy  of  a  physico-chemical  account  of  vital  activity 
becomes  even  more  obvious  when  we  pass  from  the  every- 
day activities  of  the  body  to  a  connected  series  of  animal 
activities — to  animal  behaviour. 

Let  us  return,  for  instance,  to  the  newly  hatched  micro- 
scopic larva  of  the  liver-fluke,  of  so  much  practical  import- 
ance to  sheep-farmers  (see  p.  307).  It  has  no  organs  in  the 
strict  sense  ;  it  has  only  a  few  cells  altogether  ;  it  has  no 
hint  of  a  nervous  system.  It  is  covered  with  cilia,  and 
has  energy  enough  to  swim  about  for  a  day  in  the  water- 
pools  by  the  pasture.  It  comes  in  contact  with  many 
things,  but  it  responds  to  none,  until  haply  it  touches  the 
little  freshwater  snail  (Lymnceus  truncatulus) — the  only 
contact  that  will  enable  it  to  continue  its  life.  To  this  it 
responds  by  working  its  way  in  at  the  breathing  aperture, 
and  within  the  snail  it  goes  through  a  complex  series  of 
multiplications  and  metamorphoses,  the  upshot  of  which 
may  be  that  a  sheep  becomes  infected  with  a  young  liver- 
fluke.  The  life-history  is  dramatic,  the  risks  of  failure 
are  enormous  ;  our  point  is  the  delicate  adaptation  of  a 
brainless  organism  to  the  one  stimulus  which  will  enable 
it  to  continue  its  life.  This  seems  to  us  to  be  far  beyond 
all  possibility  of  mechanical  description  ;  it  requires  a 
historical  explanation. 

What  we  have  just  alluded  to  is  no  rare  curiosity  ;  it  is 
a  frequent  and  characteristic  feature  in  animal  behaviour 
that  the  organism  is  historically  tuned  to  be  a  receptor 


FlG.  99. — Nest  of  hornet,  Vespa  crabro,  in  vertical  section.  It  was  suspended  from  a  slate 
roof,  AR.  The  top  of  the  primary  central  support  is  seen  at  T.  There  are  six  tiers  of 
combs  (1-6).  Round  the  central  comb  of  the  sixth  tier,  there  are  four  combs,  the 
structure  of  which  is  shown  at  the  side,  B  c  D  E.  V,  the  entrance.  P,  the  road  to  the 
nest,  along  the  beam  F,  is  marked  by  the  dotted  line.  A  short  cut  has  been  formed  at 
L,  which  represents  two  triangular  paper  screens.  M,  part  of  the  gable  wall.  As  the 
situation  was  a  very  warm  one,  the  wall  of  the  nest  had  only  one  thin  envelope  (ENV). 
W/fcr?Janet.) 


THE   WONDER   OF  LIFE  629 

to  particular  but  absolutely  indispensable  stimuli  which 
may  not  occur  more  than  once  in  the  life-history.  The 
freshwater  mussel,  as  we  have  already  mentioned,  carries 
her  young  ones  in  her  outer  gill- plate,  and  does  not  set 
them  free  unless  a  stickleback  or  a  minnow  or  some  other 
such  fish  is  in  the  immediate  vicinity.  When  the  fish  comes 
near,  the  mother  mussel,  whom  it  is  no  libel  to  call '  acepha- 
lous ',  liberates  a  crowd  of  pinhead-like  larval  mussels  or 
Glochidia,  who  rush  out  into  the  water  like  boys  from  the 
opened  school  door.  They  snap  their  minute  valves  ;  they 
make  for  the  fish  ;  they  fasten  on  its  skin  and  enter  upon 
a  new  chapter  of  their  life-history.  Even  in  the  laboratory, 
when  they  have  been  removed  from  the  mother,  they  be- 
come excitedly  active  if  a  morsel  of  stickleback  be  dropped 
into  the  dish  in  which  they  are.  It  is  this  organic  memory 
of  the  essential  stimulus  that  seems  to  us  to  be  character- 
istic and  supra -mechanical — of  a  higher  order  than  the 
responsiveness  of  wires  or  photographic  plates  to  particular 
kinds  of  rays.  It  is  a  sensitiveness  gained  or  invented  by 
the  creature  in  the  course  of  its  racial  evolution  and  regis- 
tered in  the  constitution.  Though  simpler,  it  is  as  well 
marked  in  the  absolutely  brainless  larva  of  the  liver-fluke 
as  in  the  larval  mussel  which  has  the  beginnings  of  a  nervous 
system ;  in  a  small-brained,  predominantly  instinctive 
creature  like  a  bee  as  much  as  in  a  big-brained,  predomin- 
ably  intelligent  creature  like  a  bird.  We  find  analogous 
kinds  of  behaviour  at  all  levels  of  nervous  organization. 
The  worker-bee  leaving  the  hive  for  the  first  time  enters 
a  new  world  with  confidence  and  proceeds  to  gather 
honey  from  difficult  flowers,  being  '  to  the  manner  born  '. 
We  have  referred  to  the  definite  proof  that  a  young 
swallow  which  leaves  Britain  for  the  South  at  the  end  of 


630  THE  WONDER  OF  LIFE 

Summer  may  return  the  following  Spring  to  the  farm- 
steading  which  was  its  birthplace.  The  question  is  : 
Does  the  return  of  the  swallow  differ  from  the  return  of  a 
thrown  boomerang  in  kind  or  only  in  degree  ;  that  is  to 
say,  Does  it  require  different  fundamental  concepts  for  its 
interpretation  ? 

We  wish  to  emphasize  the  fact  that  the  same  sort  of 
behaviour — requiring  historical  explanation — occurs  at 
all  levels  of  organization,  even  when  there  is  no  question 
of  brains  at  all.  It  is  distinct  from  the  '  soul  and  body  ' 
problem.  Dr.  Driesch,  who  stands  as  the  foremost  pro- 
tagonist of  modern  vitalism,  got  to  his  strong  convictions 
by  experiments  on  egg-cells,  where  there  are  no  data  as  to 
mental  processes.  The  problem  of  the  autonomy  of  life 
would  confront  us  even  if — to  make  an  impossible  assump- 
tion— there  were  no  animals  in  the  world  at  all,  only  plants 
and  us — Jack  and  his  bean-stalk,  in  fact. 

Migration  of  Eels. — As  an  illustration  of  the  problem 
of  vitalism  let  us  take  the  migration  of  eels,  which  has  been 
recently  discussed  in  this  connection  in  a  masterly  article  by 
Mr.  E.  S.  Russell  ('  Vitalism  ',  Rivista  di  Scienza,  April, 
1911).  It  is  a  very  useful  case,  because  the  eel  has  a  brain 
of  a  very  low  order,  and  we  are  not  warranted  in  using 
in  regard  to  it  the  psychological  terms  which  are  indis- 
pensable in  the  case  of  the  more  intelligent  birds  and 
mammals  (see  p.  458). 

The  eels  of  the  whole  of  Northern  Europe  probably  begin 
their  life  below  the  500-f athom  line  on  the  verge  of  the  deep 
sea  away  to  the  west  of  the  Hebrides  and  Ireland,  and 
southwards  to  the  Canaries.  The  early  chapters  of  the 
life-history  remain  obscure,  but  the  young  larva  rises  to 
the  upper  sunlit  waters  as  a  transparent,  sideways-flattened, 


THE   WONDER  OF  LIFE  631 

knife-blade-like  creature,  about  three  inches  in  length, 
with  no  spot  of  colour  save  in  its  eyes.  It  lives  for  many 
months  in  this  state — known  as  a  Leptocephalus — expend- 
ing energy  in  gentle  swimming,  but  taking  no  food.  It 
subsists  on  itself,  and  becomes  shorter  and  lighter,  and 
cylindrical  instead  of  blade-like.  It  is  transformed  into  a 
glass-eel,  about  two  and  a  half  inches  long,  like  a  knitting 
needle  in  girth.  It  begins  to  move  towards  the  distant 
shores  and  rivers.  In  some  cases  it  may  take  more  than 
a  year  to  reach  the  feeding  ground — those  that  ascend  the 
rivers  of  the  Eastern  Baltic  having  journeyed  over  three 
thousand  miles.  Their  ranks  are  thinned,  but  large  num- 
bers succeed  in  finding  the  estuaries,  and  the  passage  of 
millions  of  elvers  up  our  rivers  is  one  of  the  most  remark- 
able sights  of  Spring.  There  is  a  long  period  of  feeding  and 
growing  in  the  slow-flowing  reaches  of  the  rivers  and  in  the 
fish-stocked  ponds.  But  there  is  never  any  breeding  in 
fresh  water,  and  after  some  years  a  restlessness  seizes  the 
adults  as  it  seized  the  larvae — a  restlessness  due,  however, 
to  a  reproductive,  not  to  a  nutritive  motive  or  impulse. 
There  is  an  excited  return  journey  to  the  sea — they  don 
wedding  garments  of  silver  as  they  go  and  become  large 
of  eye.  They  appear  to  migrate  hundreds  of  miles,  often 
at  least  out  into  the  Atlantic  to  the  verge  of  the  deep  sea, 
where,  as  far  as  we  know,  the  individual  life  ends  in  giving 
rise  to  new  lives.  In  no  case  is  there  any  return. 

Let  us  consider  in  particular  the  penultimate  chapter,  the 
migration  from  the  rivers  to  the  distant  spawning  grounds. 
Like  many  other  fishes,  the  eel  requires  for  spawning  very 
definite  conditions  of  depth,  salinity,  and  temperature. 
The  North  Sea  will  not  serve,  for  it  is  too  shallow  ;  nor  the 
Arctic  Ocean,  for  it  is  too  cold.  What  can  the  Machine 


632  THE  WONDER  OF  LIFE 

Theory  of  Life  make  of  a  story  like  this  ?  What  can  the 
physiology  that  is  only  applied  physics  and  chemistry  tell 
us  ?  It  can  tell  us,  for  instance,  a  most  useful  thing  to  know, 
how  the  energy  for  the  journey  is  obtained  from  chemical 
explosions  of  oxidizable  material  in  the  muscles  of  the  eel's 
body.  It  can  tell  us  some  of  the  steps  in  the  making  of  this 
fuel  out  of  the  eel's  food.  It  can  tell  us  that  the  muscles 
are  kept  rhythmically  contracting  by  nervous  stimuli ; 
that  the  advent  of  sex-maturity  often  alters  an  animal's 
reactions  to  external  stimuli ;  and  so  on  for  a  whole  volume. 
It  is  all  interesting  and  indispensable,  but  it  does  not  really 
help  us  much  in  trying  to  understand  the  migration  of  the 
eels  to  the  distant  spawning  grounds.  Even  if  an  omnis- 
cient chemist  and  physicist  could  give  an  account  in  his 
own  language  of  all  the  physical  and  chemical  happenings 
that  occur  in  the  eel's  body  from  the  time  it  left  the  pond 
to  the  day  of  its  death,  that  would  not  make  more  intelli- 
gible to  the  biologist  the  concatenation  of  all  these  into  the 
unified  adventure  of  migration. 

'  To  the  chemist ',  Kussell  says,  '  confronted  with  this 
problem,  there  is  no  fact  of  migration  at  all ;  there  is  only 
an  intricate  enravelment  of  chemical  reaction.  To  the 
biologist  the  fact  of  migration  to  a  particular  region  for  a 
particular  purpose  is  cardinal '. 

If  it  be  said  that  one  can  picture,  in  dreams  at  least,  a 
torpedo  so  delicately  adjusted,  that  it  descended  rivers, 
went  out  to  sea,  kept  off  the  rocks,  turned  corners,  and  did 
not  explode  until  it  could  do  so  effectively  in  an  area  of 
appropriate  stimulation,  the  answer  must  be  that  this 
mechanism  is  still  a  very  hypothetical  construction,  and 
that  if  it  were  constructed  it  would  not  be  a  fair  sample  of 


THE  WONDER  OF  LIFE  633 

the  inorganic  world.  For  obviously  it  would  have  a  human 
idea  and  a  human  purpose  inside  of  it — the  very  essence 
of  its  construction.  But  more  than  that,  the  eel  has  made 
itself  what  it  is  in  the  course  of  ages  ;  it  has  traded  with 
time ;  it  has  evolved.  And  again,  the  hypothetical 
torpedo  does  not,  in  its  final  explosion,  start  a  crowd  of 
potential  torpedoes,  which  is  what  the  eels  do  before  they 
die. 

But  if  the  mechanistic  account  of  the  eel's  migration  is 
unsatisfactory,  is  the  vitalistic  one — or,  as  we  prefer  to  say, 
the  biological  one — any  better  ?  What  light  has  biology 
to  throw  on  the  remarkable  story  ?  Only  this,  that  we 
can  relate  the  particular  case  of  the  eel  to  what  we  know  of 
organisms  in  general,  that  they  are  historical  beings,  deter- 
mined by  their  past — their  own  past  and  that  of  their  race. 
The  eel's  inheritance  is  a  treasure-store  of  the  ages,  a 
registration  of  many  inventions.  Non-living  things  have 
no  history  in  this  sense  ;  we  cannot  say  that  they  have 
profited  by  experience.  In  the  organism,  as  Bergson 
says,  the  past  is  prolonged  into  the  present.  Thus  we  pass 
on  to  a  new  level  of  explanation  or  interpretation,  which  is 
historical — in  a  sense  different  from  that  implied  when  we 
give  a  so-called  historical  interpretation  of  the  present 
state  of  the  Alps.  As  Professor  W.  K.  Clifford  put  it  :— 

*  It  is  the  peculiarity  of  living  things  not  merely  that 
they  change  under  the  influence  of  surrounding  circum- 
stances, but  that  any  change  that  takes  place  in  them  is 
not  lost  but  retained,  and  as  it  were  built  into  the  organism 
to  serve  as  the  foundation  for  future  actions.  .  .  .  No 
one  can  tell  by  examining  a  piece  of  gold  how  often  it  has 
been  melted  and  cooled  in  geologic  ages.  .  .  .  Any  one 
who  cuts  down  an  oak  can  tell  by  the  rings  in  its  trunk 


634  THE  WONDER  OF  LIFE 

how  many  times  winter  has  frozen  it.  ...  A  living  being 
must  always  contain  within  itself  the  history,  not  merely 
of  its  own  existence,  but  of  all  its  ancestors.' 

As  Bergson  maintains,  it  is  distinctive  of  the  organism, 
as  of  ourselves,  that : — 

'  Its  past,  in  its  entirety,  is  prolonged  into  its  present, 
and  abides  there,  actual  and  acting '.  '  Continuity  of 
change,  preservation  of  the  past  in  the  present,  real  dura- 
tion— the  living  organism  seems  to  share  these  attributes 
with  consciousness '. 

Argument  from  Development. — When  we  observe 
the  development  of  an  animal  actually  going  on,  in  almost 
perfect  transparency,  as  in  the  moth  Botys  hyalinalis,  we 
get  an  impression  of  something  very  unlike  anything  else  in 
the  world.  From  a  minute  clear  drop  of  living  matter 
lying  on  the  top  of  the  yolk  we  see  in  the  course  of  twenty- 
one  days  the  development  of  the  chick — the  gradual  emer- 
gence of  the  obviously  complex  from  the  apparently  simple. 
It  seems  far  away  from  mere  machinery  ;  it  is  more  like 
an  artist  painting  a  picture.  We  get  the  same  impression 
when  we  look  into  details,  such  as  the  making  of  the  silk- 
like  threads  that  compose  the  familiar  skeleton  of  the  bath 
sponge.  Large  numbers  of  secretory  cells  called  spongo- 
blasts  group  themselves  in  double  file  in  the  middle 
stratum  of  the  sponge,  as  if  some  unseen  captain  mar- 
shalled them.  Up  the  middle  of  the  double  file  spongin 
is  secreted,  made  at  the  expense  of  the  contributors,  and 
the  many  individual  contributions  coalesce  in  a  sponge- 
fibre.  By  combining  the  images  that  we  get  from  sections 
at  various  stages  we  can,  in  a  sense,  see  the  replacement 
of  a  piece  of  cartilage  by  bone — the  sappers  and  miners 


THE  WONDER  OF  LIFE  635 

called  osteoclasts  who  clear  the  ground,  and  the  builders 
called  osteoblasts  who  build  up  the  new  construction — all 
working  like  busy  ants.  We  feel  that  this  transcends 
mechanical  categories.  Eeference  has  already  been  made 
to  the  quite  extraordinary  series  of  events  that  is  witnessed 
when  a  larval  insect,  such  as  a  fly,  goes  through  its  meta- 
morphosis— the  larval  body  breaking  down  into  debris,  the 
new  body  being  built  up  out  of  the  ruins  on  a  very  different 
architectural  plan.  The  central  wonder  of  development 
is  the  general  process  of  differentiation,  the  realization 
of  the  inheritance,  but  this  is  enhanced  by  many  accessory 
facts  :  there  is  the  remarkable  power  the  embryo  often 
shows  of  righting  itself  when  the  building  materials  of  its 
edifice  have  been  artificially  disarranged ;  there  are  interest- 
ing '  regulation  phenomena  '  by  which  it  adjusts  itself  after 
disproportions  have  been  artificially  induced ;  there  are 
the  strangely  circuitous  paths,  reminiscent  of  ancient  his- 
tory, by  which  it  reaches  its  goal ;  there  are  the  widely 
different  ways  of  securing  the  same  results. 

The  vitalistic  argument  from  the  facts  of  development 
has  found  its  finest  expression  in  the  work  of  Dr.  Hans 
Driesch,who  was  led  to  the  conclusions  of  his  Science  and 
Philosophy  of  the  Organism  by  a  brilliant  series  of  embryo- 
logical  experiments.  His  arguments  based  on  the  study 
of  morphogenesis,  or  the  development  of  form  and  structure, 
are  too  technical  for  our  present  discussion  (we  have  given 
a  resume  of  them  in  The  Hibbert  Journal,  January,  1912, 
in  an  article  from  which  we  have  borrowed  freely) ;  we 
cannot  do  more  than  indicate  his  main  thesis. 

'  Life,  at  least  morphogenesis,  is  not  a  specialized 
arrangement  of  inorganic  events  ;  biology,  therefore,  is 
not  applied  physics  and  chemistry  :  life  is  something  apart, 


636  THE  WONDER  OF  LIFE 

and  biology  is  an  independent  science  '....'  There  is 
something  in  the  organism's  behaviour — in  the  widest 
sense  of  the  word — which  is  opposed  to  an  inorganic  resolu- 
tion of  the  same,  and  which  shows  that  the  living  organism 
is  more  than  a  sum  or  an  aggregate  of  its  parts.  .  .  .  This 
something  we  call  "  Entelechy  ".' 

Driesch  conceives  of  '  Entelechy  '  as  '  an  agent  at  work 
in  nature  ',  'of  a  non-spatial  nature  ',  without  a  seat  or 
localization  ;  it  is  unmaterial,  and  it  is  not  energy  ;  it  is 
not  inconsistent  in  its  agency  with  the  laws  of  energetics  ; 
its  function  is  to  suspend  and  set  free,  in  a  regulatory  man- 
ner, pre-existing  potentials,  i.e.  pre-existing  faculties  of 
inorganic  interaction. 

Argument  from  Organic  Evolution. — It  is  con- 
venient to  speak  of  '  cosmic  evolution ',  '  inorganic  evolu- 
tion ',  '  the  evolution  of  the  solar  system  ',  '  the  evolution 
of  the  earth  ',  '  the  evolution  of  scenery  ',  and  so  on ;  but 
there  is  a  risk  of  identifying  processes  which  are  really 
very  different. 

In  biology  it  is  usual  to  draw  a  distinction  between  the 
two  terms — development  and  evolution.  Development 
(Haeckel's  ontogeny)  is  the  becoming  of  the  individual ; 
Evolution  (Haeckel's  phylogeny)  is  the  becoming  of  the 
race.  How  do  these  agree  and  differ  ?  In  both  there  is 
a  succession  of  stages,  and  the  scientific  assumption  is  that 
each  stage  is  conditioned  by  the  preceding  stages.  In 
development  the  continuity  between  successive  stages  is 
one  of  personal  identity ;  it  is  the  same  organism  from 
start  to  finish,  though,  as  we  have  seen  in  the  chapter  on 
'  The  Cycle  of  Life  ',  there  are  some  apparent  contradic- 
tions. In  racial  evolution,  however,  the  stages  are  physic- 
ally discontinuous.  Although  we  speak  of  the  continuity 


THE  WONDER  OF  LIFE  637 

of  the  germ-plasm,  we  must  admit  that  one  generation 
is  not  personally  identical  with  preceding  or  succeeding 
generations. 

But  the  radical  difference  is  surely  this,  that  in  any  stage 
in  racial  evolution  there  are  numerous  individuals  that  do 
not  figure  in  the  final  result ;  they  are  outside  the  pale  of 
success  ;  they  die  before  their  time  or  they  have  small 
families  ;  in  any  case  they  and  theirs  are  eliminated  in 
Nature's  sifting.  They  do  not  count.  They  are  '  cast  as 
nothing  to  the  void  '.  It  is  easy  enough  to  find  in  some  in- 
dividual life-histories,  complicated  by  metamorphosis  and 
the  like,  instances  of  the  suppression  or  elimination  of  parts, 
but  there  is  nothing  in  development  comparable  to  the 
staking  of  individual  lives  and  losing  of  them  that  has 
gone  on  throughout  the  whole  of  that  sublime  and  romantic 
adventure  which  we  call  organic  evolution. 

It  seems  to  us  therefore  that  it  would  be  more  accurate 
to  speak  of  the  development  of  the  earth,  the  development 
of  the  solar  system,  and  so  on,  keeping  the  term  evolution 
for  the  organic  and  the  super- organic.  Better  still  would 
it  be  to  find  another  term  for  the  sequence  of  changes  in  an 
inorganic  system  ;  and  some  distinguished  men  of  science 
have  recognized  this  in  speaking  of  '  the  story  of  the 
heavens ',  '  the  story  of  the  earth  ',  and  so  forth. 

This  question  of  words  matters  a  good  deal.  As  Hobbes 
finely  said,  words  are  only  intellectual  counters  with  which 
the  wise  do  reckon,  but  they  are  the  money  of  fools ; 
yet  words  make  fools  of  us  all.  The  fundamentally  im- 
portant thing  is  to  avoid  verbally  identifying  processes 
which  are  really  very  different.  In  the  succession  of  inor- 
ganic changes,  there  are  no  alternatives  ;  every  stage  is  the 
necessary  outcome  of  its  antecedents  ;  all  is  mechanically 


638  THE  WONDER  OF  LIFE 

determined ;  the  chains  are  of  iron.  In  the  succession 
of  organic  changes  there  are  alternatives,  as  a  species  may 
show  in  splitting  into  two  or  more  equally  successful 
species  ;  the  creatures  are  genuine  agents  in  a  fashion 
quite  different  from  that  of  streams  of  water  or  ice  which 
diverge  and  combine ;  in  short,  the  mechanical  categories 
are  transcended.  We  are  not  unaware  of  the  analogies 
between  the  inorganic  sequence  of  changes  and  the  evolu- 
tion of  organisms  that  have  often  been  indicated,  and  that 
Herbert  Spencer  made  much  of ;  they  are  fascinating 
but  unconvincing.  It  is  said,  for  instance,  that  '  the 
process  by  which  worlds  emerge  from  the  primal  nebula 
depends  upon  the  conflict  of  attractive  and  repulsive 
forces  ',  just  as  the  process  by  which  species  emerge  from  a 
primal  stock  depends  upon  the  struggle  for  existence.  But 
'  the  conflict  of  attractive  and  repulsive  forces  '  is  a  phrase 
which  must  be  used  in  a  large  and  metaphorical  sense — 
which  is  what  Darwin  said  in  reference  to  the  phrase 
'  struggle  for  existence  '. 

What  we  have  in  the  realm  of  organisms  is  a  continual 
creation  and  experimenting  on  the  one  hand,  and  a  con- 
tinual sifting  on  the  other,  but  the  sifting  is  often  a  very 
gentle  process.  At  the  best,  in  comparing  inorganic  and 
organic  '  evolution ',  we  do  not  get  beyond  formal  re- 
semblances. 

The  reasons  why  many  biologists  cannot  accept  as 
adequate  any  mechanical  description  of  organic  evolution 
centre  in  the  nature  of  the  organism.  The  organism  plays 
such  an  active  part.  It  is  active  in  its  variations,  which  are 
experiments  in  self-expression,  though  some  environmental 
stimulus  may  pull  the  trigger  which  liberates  them.  It  is 
in  some  measure  active  even  in  the  process  of  natural 


THE  WONDER   OF  LIFE  639 

selection,  for  it  does  not  simply  submit  to  the  apparently 
inevitable.  It  often  evades  its  fate  by  a  change  of  policy 
or  of  environment ;  it  compromises,  it  experiments  ;  it 
is  full  of  device  and  endeavour.  It  is  certainly  much  more 
than  a  pawn  in  the  hands  of  Fate  or  Environment ;  it 
plays  its  own  game.  Besides  the  variability  or  inventive- 
ness, which,  from  the  germ-cells  outwards,  offers  solutions 
to  life's  problems,  there  is  the  organism's  utilisation  of  these 
assets,  and  there  is  the  equally  fundamental  entailment  or 
hereditary  registration  of  the  successful  new  departures 
without  which  evolution  were  impossible. 

The  Continuity  of  Evolution. — Immense  gaps  in  our 
knowledge  are  immediately  apparent  when  we  inquire 
into  the  origin  of  living  organisms  upon  the  earth,  the 
beginnings  of  intelligent  behaviour,  the  origin  of  Verte- 
brates, the  emergence  of  Man,  and  so  on.  We  know  very 
little  as  yet  in  regard  to  the  way  in  which  any  of  the  '  big 
lifts  '  in  evolution  have  come  about,  and  yet  we  believe 
in  the  continuity  of  the  process.  That  is  implied  in  our 
ideal  concept  of  evolution,  which  we  accept  as  a  working 
hypothesis.  It  is  not  very  easy  to  say  what  it  is  that  is 
continuous,  but  we  mean  in  part  that  there  is  at  no  stage 
any  intrusion  of  extraneous  factors.  But  this  continues 
to  raise  in  the  minds  of  many  the  difficulty  that  the  results 
seem  much  too  large  for  their  antecedents.  Can  we  believe 
that  the  world  of  life,  with  its  climax  in  Man,  has  been 
evolved  from  a  nebulous  mass  ? 

Let  us  recall  Huxley's  famous  statement  of  his  radical 
mechanism  : — 

'  If  the  fundamental  proposition  of  evolution  is  true, 
namely,  that  the  entire  world,  animate  and  inanimate,  is 
the  result  of  the  mutual  interaction,  according  to  definite 


640  THE  WONDER  OF  LIFE 

laws,  of  forces  possessed  by  the  primitive  nebulosity  of  the 
universe,  then  it  is  no  less  certain  that  the  present  actual 
world  reposed  potentially  in  the  cosmic  vapour,  and  that 
an  intelligence,  if  great  enough,  could,  from  his  knowledge 
of  the  properties  of  the  molecules  of  that  vapour,  have 
predicted  the  state  of  the  fauna  in  Great  Britain  in  1888 
with  as  much  certitude  as  we  say  what  will  happen  to 
the  vapour  of  our  breath  on  a  cold  day  in  winter'. 

This  strong  and  confident  statement  includes  several 
assumptions  regarding  which  one  may  fairly  argue.  Thus 
Professor  Bergson  calls  attention  to  its  practical  denial 
that  time  really  counts.  '  In  such  a  doctrine,  time  is  still 
spoken  of ;  one  pronounces  the  word,  but  one  does  not 
think  of  the  thing.  For  time  is  here  deprived  of  efficacy, 
and  if  it  does  nothing,  it  is  nothing  '.  Huxley  practically 
denies  the  creative  individuality  of  organisms  which  trade 
with  time  in  a  spontaneous  and  unpredictable  way  all  their 
own. 

The  '  fundamental  proposition  of  evolution '  (which 
Huxley  invoked)  is  of  Man's  own  making,  and  we  are  not 
inclined  to  be  coerced  by  it  into  believing  that  the  state 
of  the  British  fauna  either  in  1888  or  in  1914  could  have 
been  predicted  by  any  intelligence  however  great  from  a 
*  knowledge  of  the  properties  of  the  molecules '  of  the 
cosmic  vapour.  Not  only  because  we  believe  that  time 
counts  with  living  creatures,  but  because  molecules  and 
the  like  are  concepts  of  physical  science  used  for  the  de- 
scription of  certain  abstracted  aspects  of  reality — used  to 
describe  things  for  a  particular  purpose  or  from  a  certain 
point  of  view.  It  is  true  that  they  correspond  to  that 
aspect  of  reality  so  accurately  that  we  risk  lives  and 
fortunes  on  them,  but  to  say  that  they  exhaust  the  reality 


THE  WONDER  OF  LIFE  641 

appears  to  us  not  only  an  unwarrantable  assumption,  but 
a  contradiction  in  terms. 

The  '  primitive  nebulosity  of  the  universe  ',  or  of  our 
solar  system  at  any  rate,  has  probably  its  analogues  in  the 
heavens  of  to-day,  where  worlds  can  be  seen  a-making. 
As  far  as  its  movements  and  condensations  and  such 
like  went,  it  might  have  been  physically  described,  and 
it  could  not  have  been  described  in  any  other  way. 
But  if  within  that  whirling  sea  of  molecules  there  '  re- 
posed potentially  the  present  actual  world',  then  the 
physical  description  would  not  have  been  the  whole  truth 
about  it.  Yet  we  do  not  know  how  the  physicist  could 
have  indicated  that  his  description  was  not  exhaustive. 
Whenever  we  think  of  facts  like  intelligent  behaviour 
among  animals  or  the  reasoned  discourse  of  Man,  who  has 
harnessed  electricity  to  his  chariot,  has  made  the  ether  carry 
his  messages,  has  annihilated  distance,  has  coined  wealth 
out  of  the  thin  air,  and  has  begun  to  control  heredity 
itself,  we  feel  that  if  these  qualities  reposed  potentially  in 
the  nebula's  whirling  sea,  the  physical  description  which 
might  have  been  given  could  not  have  been  exhaustive. 
Rather  would  we  fall  back  on  the  fundamental  proposition 
of  evolution  which  Aristotle  discerned,  That  there  is  no- 
thing in  the  End,  which  was  not  also,  in  its  quality, 
in  the  Beginning.  Our  philosophical  position  is  briefly, 
That  in  the  Beginning  was  the  Logos. 

Bergson's  View. — The  two  modern  thinkers  who  have 
most  appreciated  the  wonder  of  life — that  is  to  say,  the 
relation  of  theory  of  life  and  theory  of  knowledge — are 
Professors  Henri  Bergson  and  Hans  Driesch.  We  have 
already  referred,  in  a  necessarily  inadequate  way,  to 
Driesch's  rehabilitation  of  the  Aristotelian  conception  of 

T  T 


642  THE  WONDER  OF  LIFE 

Entelechy ;  we  venture  to  refer — it  must  be  very  inade- 
quately again — to  Bergson's  conception  of  the  origin  and 
nature  of  life.  Bergson's  metaphysical  theory  is  that  a 
broad  current  of  consciousness  penetrated  matter,  carrying 
matter  along  to  organization.  He  does  not  keep  us  in 
doubt  as  to  what  he  means  by  life.  Life  is  conscious- 
ness launched  into  matter — '  availing  itself  of  a  slight 
elasticity  in  matter  ',  '  using  matter  for  its  own  purposes  '. 
Consciousness,  or  rather  supra-consciousness,  is  at  the 
origin  of  life,  and  consciousness  appears  as  the  motive 
power  in  evolution.  '  Consciousness,  or  supra-conscious- 
ness,  is  the  name  for  the  rocket  whose  extinguished  frag- 
ments fall  back  as  matter  ;  consciousness,  again,  is  the 
name  for  that  which  subsists  of  the  rocket  itself,  passing 
through  the  fragments  and  lighting  them  up  into  organisms. 
But  this  consciousness,  which  is  a  need  of  creation,  is  made 
manifest  to  itself  only  where  creation  is  possible.  It  lies 
dormant  when  lif  e  is  condemned  to  automatism  ;  it  wakens 
as  soon  as  the  possibility  of  choice  is  restored  '.  In  fact 
an  organism  is  conscious  in  proportion  to  its  power  to  move 
freely — a  quaint  metaphysical  apology  for  athletics.  In 
the  course  of  evolution  it  becomes  more  and  more  free  as 
the  sensori-motor  system  becomes  more  perfect.  '  But, 
everywhere  except  in  man,  consciousness  has  let  itself  be 
caught  in  the  net  whose  meshes  it  tried  to  pass  through  : 
it  has  remained  the  captive  of  the  mechanisms  it  has  set 
up '.  With  man,  however,  a  new  freedom  began.  Con- 
sciousness is  breaking  its  chains.  How  free  it  may  become, 
who  shall  say  ? 

A  Suggestion. — Under  the  sway  of  his  evolution-idea, 
the  biologist  finds  it  difficult  to  entertain  the  hypothesis  of 
consciousness  being  launched  into  matter  as  a  bolt  from 


THE  WONDER  OF  LIFE  643 

the  blue.  May  it  not  have  been  that  the  anima  animans 
has  been  with  creation  through  and  through,  and  from 
first  to  last  ?  We  think  of  the  majestic  order  of  the  heavens 
and  the  perfection  of  the  dew-drop,  of  the  extraordinary 
surge  of  our  whole  solar  system  towards  some  unknown 
goal,  and  of  the  internal  '  life  '  of  crystals.  We  wonder 


FIG.  100. — Rings  formed  by  placing  a  drop  of  80  per  cent,  silver 
nitrate  on  a  thin  layer  of  5—10  per  cent .  gelatine,  which  contains 
about  O'l  percent,  of  potassium  bichromate.  The  gelatine  under 
the  drop  is  coloured  red-brown,  silver  chromate  being  precipitated. 
Outside  that  a  dull,  white  margin  is  formed  which  spreads  slowly 
outwards.  As  the  diffusion  goes  on  the  rings  of  similar  precipitation 
of  silver  chromate  are  formed  at  a  little  distance  beyond  the  area  of 
uniform  precipitation.  (After  Liesegang.) 

if  Time  has,  after  all,  simply  flowed  over  the  opal  and  the 
agate,  and  whether  the  beryl  has  garnered  no  fruits  of 
experience.  A  photograph  of  a  zoophyte — e.g.  Sertularia 
cupressina — is  extraordinarily  like  the  beautiful  dendritic 
frescoes  which  imprisoned  Manganese  makes  on  the  wall  of 
its  cell !  To  take  another  example,  we  admire  the  intricate 
zonal  structure  of  Liesegang's  rings — formed,  for  instance, 


644  THE  WONDER  OF  LIFE 

when  a  big  drop  of  silver  nitrate  is  placed  on  a  film  of 
gelatine  in  which  there  is  a  trace  of  potassium  bichromate. 
There  we  see,  as  the  diffusion  and  precipitation  proceed, 
the  rings  of  growth  on  a  salmon's  scale  and  the  zones  of  the 
otolith  in  his  ear.  There  we  see,  as  the  diffusion  and  pre- 
cipitation continue,  the  zones  of  growth  in  the  stem  of  an 
oak,  in  the  recesses  of  a  pearl,  in  the  vertebra  of  a  fish,  on 
the  scale  of  a  tortoise,  and  on  the  barred  feather  of  the 
hawk.  No  doubt  a  wide  gulf  is  fixed,  but  the  phenomena 
are  extraordinarily  similar  as  well  as  very  different,  and 
our  point  is  simply  that  too  much  must  not  be  made  of  the 
quality  of  '  inertness '  in  non-living  material. 

May  it  not  be  that  an  aspect  of  reality  continuous  with 
the  clear  consciousness  in  the  higher  reaches  of  life  has 
always  been  present,  though  it  is  negligible  for  the  practical 
purposes  of  science  until  the  confines  of  the  inorganic  are 
passed  ?  May  it  not  be  allowing  us  glimpses  of  its  presence 
in  the  architecture  of  the  crystal,  in  the  hidden  '  life '  of 
jewels,  and  in  radio-activity  ?  May  it  not  be  expressing 
itself  in  the  tendency  that  matter  has  to  complexify — pass- 
ing from  atom  to  molecule,  from  simple  molecule  to  com- 
plex molecule,  and  from  molecule  to  colloid  masses  ?  May 
it  not  lie  behind  the  inorganic  evolution  which  we  are 
beginning  to  discover  ?  May  it  not  have  been  resident 
in  the  nebula  of  our  solar  system,  and  be  contemporaneous 
with  the  primeval  Order  of  Nature. 

IN  CONCLUSION 

A  consideration  of  the  everyday  functions  of  organisms, 
of  their  behaviour,  of  their  development,  and  of  their 
evolution,  leads  us  away  from  Kant's  view  that  there  is 
one  science  of  nature,  and  leads  us  to  follow  Driesch  and 


THE  WONDER  OF  LIFE  645 

others  in  maintaining  that  Biology  must  be  ranked  beside 
Physics  as  a  fundamental  and  autonomous  science.  An- 
other line  of  argument  would,  we  believe,  lead  us,  even 
from  the  naturalist's  point  of  view,  to  recognize  the  auto- 
nomy of  Psychology. 

We  recognize,  then,  three  orders  of  facts  :  the  physical 
order,  where  mechanism  reigns,  where  mechanical  formulae 
suffice  for  the  description  of  what  goes  on ;  the  animate 
order,  where  mechanism  is  transcended  ;  and  the  psychical 
order,  where  mechanism  is  irrelevant.  It  is  plain  that  the 
physical  order  overlaps  the  animate  order,  for  organisms 
are  material  systems,  and  their  life  includes  a  concatena- 
tion of  chemico-physical  processes.  At  the  same  time,  as 
we  have  seen,  we  cannot  explain  the  fundamental  pro- 
perties of  the  organism,  which  we  start  with  in  biology,  in 
chemico-physical  terms,  nor  would  a  complete  chemico- 
physical  description  of  what  goes  on  in  the  life  of  the 
organism  be  the  kind  of  description  which  a  biologist  seeks. 
The  same  applies  to  the  psychical  order,  which  is  overlapped 
by  the  biological.  In  short,  the  sciences  are  differentiated 
not  only  by  their  subject  matter,  but  by  their  characteristic 
questions  and  methods  and  concepts. 

Perhaps  we  may  be  allowed  to  refer  to  three  remarks 
which  are  often  made  in  regard  to  this  sort  of  discussion 
by  the  plain  man  in  the  street,  from  whom  most  of  us,  after 
all,  are  not  far  removed.  He  is  surprised,  in  the  first 
place,  at  the  longevity  of  the  problem  of  vitalism  and  the 
oscillations  of  human  judgment  from  one  side  to  another. 
An  old  question  indeed,  for  Aristotle  was  a  thorough-going 
vitalist,  and  his  biology  was  in  conscious  opposition  to  the 
school  of  Democritus.  And  from  that  time  we  have  had 
periodic  oscillations  between  vitalistic  and  mechanistic 


646  THE  WONDER  OF  LIFE 

interpretations.  Now  the  organism  is  a  machine,  and 
again  it  is  a  spirit ;  now  it  is  a  free  agent,  and  again  it  is 
only  an  automaton  ;  now  engine  and  again  entelechy. 

There  are  several  reasons  for  this  continual  see-saw,  the 
chief  one  being  that  there  is  truth  on  both  sides.  For  the 
purposes  of  chemistry  and  physics  the  organism  may 
be  adequately  considered  as  a  material  system  ;  for  the 
purposes  of  biology  another  aspect  of  its  reality  has  to  be 
recognized. 

But  another  reason  is  given  by  Bergson  in  his  theory 
of  the  limitation  of  our  intellect.  '  The  intellect,  so  skilful 
in  dealing  with  the  inert,  is  awkward  the  moment  it  touches 
the  living  '.  '  It  is  characterized  by  a  natural  inability 
to  comprehend  life  '.  '  Created  by  life,  in  definite  circum- 
stances, to  act  on  definite  things,  how  can  it  embrace  life, 
of  which  it  is  only  an  emanation  or  an  aspect  ?  Deposited 
by  the  evolutionary  movement,  in  the  course  of  its  way, 
how  can  it  be  applied  to  the  evolutionary  movement  it- 
self ?  '  'In  vain  we  force  the  living  into  this  or  that  one 
of  our  intellectual  moulds.  All  the  moulds  crack.' 

What  then  can  be  done  ?  Some  would  say,  '  Nothing  ! 
Let  us  cultivate  our  garden '.  Bergson's  suggestion  is, 
that  our  method  of  pure  intellectualism  is  wrong.  The 
line  of  evolution  that  ends  in  human  intelligence  is  not 
the  only  one.  Other  forms  of  consciousness,  such  as 
instinct,  '  express  something  that  is  immanent  and  essential 
in  the  evolutionary  movement.  Have  we  not  powers 
complementary  to  the  understanding  by  which  we  may 
get  a  vision — a  fleeting  vision — of  what  life  essentially  is  '  ? 
We  have  a  fringe  of  instinct. 

Some  of  the  tough-minded,  or  we  ourselves  in  tough- 
minded  moods,  are  apt  to  depreciate  that  '  fringe  of  vague 


THE  WONDER  OF  LIFE  647 

intuition  that  surrounds  our  distinct — that  is,  intellectual 
— representation  '.  According  to  Bergson  it  is  an  invalu- 
able organon. 

In  sympathy,  in  artistic  and  poetic  feeling,  we  come  near 
instinct.  We  speak  of  the  intuitive  insight  of  the  '  born 
doctor '  and  the  divining  sympathy  of  the  mother.  Berg- 
son  says  that  we  do  well  so  to  speak.  '  Instinct  is  sym- 
pathy ;  if  it  could  extend  its  object  and  also  reflect  upon 
itself,  it  would  give  us  the  key  to  vital  operations — just  as 
intelligence  guides  us  into  matter  '.  'By  intuition  ',  he 
says,  '  I  mean  instinct  that  has  become  disinterested,  self- 
conscious,  capable  of  reflecting  upon  its  object,  and  of 
enlarging  it  indefinitely  '.  It  brings  us  sympathetically 
into  life's  own  domain,  and  makes  us  feel  sure  once  more 
that  Wordsworth,  Emerson,  Meredith,  and  other  nature- 
poets  are  truest,  because  deepest,  biologists  of  us  all. 

In  the  second  place,  the  plain  man  wonders  why  we  should 
worry  over  such  an  academic  question  as  the  number  of 
the  sciences.  Vitalist  or  mechanist — a  plague  o'  both  your 
houses  ! — will  either  view  make  any  difference  to  this  life 
of  mine  ?  This  raises  large  questions,  but  one  answer  must 
suffice.  If  the  mechanistic  theory  of  the  organism  be 
erroneous — a  false  simplicity  or  materialism — it  behoves 
us  in  the  love  of  truth  to  fight,  all  the  more  that  those 
who  maintain  that  biology  is  only  applied  chemistry  and 
physics  are  of  the  company  of  those  who  say  that  psycho- 
logy is  a  branch  of  physiology  and  sociology  a  pseudo- 
science.  This  position  may  be  held  with  conviction  in  the 
name  of  scientific  method  and  interpretation  by  men  who 
are  as  much  impressed  as  any  with  the  fundamental 
mysteriousness  of  nature,  but  it  tends  with  the  careless 
to  strengthen  the  hands  of  the  unpoetic,  the  unromantic, 


648  THE  WONDER  OF  LIFE 

and  the  wonderless,  who  darken  the  eyes  of  their  under- 
standing. 

In  the  third  place,  the  plain  man  says :  *  This  big  talk 
about  the  autonomy  of  the  organism,  and  so  forth,  is  all  very 
well,  but  do  you  mean  that  there  is  in  the  living  creature 
more  than  meets  the  eye  ?  Is  there  more  than  matter  and 
energy,  or  not  ?  '  The  disappointing  scientific  answer  must 
be  that  the  question  is  not  rightly  put.  We  do  not  know 
what  matter  really  is,  nor  what  all  the  energies  of  matter 
may  be.  What  we  do  know  is  that  present-day  physico- 
chemical  formulae  do  not  suffice  for  the  biological  descrip- 
tions of  organisms,  and  that  we  require  to  use  historical 
explanations  which  are  beyond  the  limits  of  physics  and 
chemistry.  And  we  find  no  warrant  for  asserting  that  the 
physical  concepts  of  '  matter  '  and  '  energy  ',  abstracted 
off  for  particular  scientific  purposes,  exhaust  the  reality  of 
Nature.  Very  much  the  reverse. 

We  see  before  us  an  ascending  series  of  individualized 
activities  correlated  with  an  increasing  complexity  of 
material  organization — the  two  aspects  are  inseparable  : 
the  worm  is  a  higher  synthesis  than  the  mineral,  and  the 
bird  than  the  worm,  but  we  cannot  explain  the  fundamental 
properties  of  these  successive  syntheses  in  terms  of  anything 
else.  We  feel  sure,  however,  that  organisms  reveal  or 
express  a  deeper  aspect  of  reality  than  crystals  do  (deeper, 
because  it  is  nearer  to  what  is  most  real  to  ourselves,  our 
own  conscious  experience),  and  that  in  this  sense  there 
is  more  in  the  plant  than  in  the  crystal,  more  in  the  animal 
than  in  the  plant,  more  in  the  bird  than  in  the  worm,  and 
more  in  man  than  in  them  all, 

FINIS 


[From  Huxley's  translation  of  Goethe's  Aphorisms.] 

IHature !  "Ode  are  surrounDeD  anD  embraced  bg  ber : 
powerless  to  separate  ourselves  trom  ber,  anD  powerless 
to  penetrate  begonb  ber.  .  .  . 

TUfle  live  in  ber  miDst  ano  know  ber  not.  Sbe  ts  incess* 
antlg  speaking  to  us,  but  betrays  not  ber  secret.  .  .  . 

Sbe  rejoices  in  illusion.  Idboso  Destroys  it  in  bimself 
ano  otbers,  bim  sbe  punisbes  witb  tbe  sternest  tgrannp.. 
Wboso  follows  ber  in  faitb,  bim  sbe  takes  as  a  cbilD  to  ber 
bosom. 

Sbe  wraps  man  in  Darkness,  ano  makes  bim  for  ever 
long  for  ligbt.  Sbe  creates  bim  DepenDent  upon  tbe  eartb, 
Dull  ano  beavg ;  ano  set  is  always  sbaking  bim  until  be 
attempts  to  soar  above  it.  ... 

$  praise  ber  ano  all  ber  works. 

Sbe  bas  brougbt  me  bere  anD  will  also  leaD  me  awap.. 
5  trust  ber.  Sbe  mag  scolo  me,  but  sbe  will  not  bate  ber 
work.  5t  was  not  5  wbo  spoke  of  ber.  IRo !  trabat  is  false 
anD  wbat  is  true,  sbe  bas  spoken  it  all.  Gbe  fault,  tbe  merit, 
is  all  bers.  .  .  . 

Bverp.  one  sees  ber  in  bis  own  fasbion.  Sbe  bioes  unoer 
a  tbousano  names  anD  pbrases,  anD  ts  always  tbe  same. 

5  praise  ber  anD  all  ber  works.  Sbe  is  silent  anD  wise.  5 
trust  ber. 


649 


INDEX 


Abundance     of     individuals,     7 ; 

of  life,  104 
Abyssal  fauna,  81 
Acacias,  experiments  with,  160 
Acorn-shells,  448 
Acquired   characters,    transmissi- 

bility  of,  595 
Adaptations,      509 ;      Darwinian 

theory     of,    515 ;     Lamarckian 

theory  of,  515  ;  in  deep  sea,  90  ; 

of    freshwater    animals,     107 ; 

functional,     530 ;      illustrations 

of,    518  ;    limitations   of,    128  ; 

nature  of,  514  ;   origin  of,  515  ; 

spoiling,  279-280  ;  of  terrestrial 

animals,  120 
Aerial  fauna,  123 
Agar,  Dr.  W.  E.,  149,  596-601 
Agassiz,  Alexander,  82 
Alcock,  Prof.,  158,  289 
Alpine  swifts,  142 
Ambrosia,  282 

Amphibians,   importance   of,   118 
Anableps,  528 
Anaphylaxis,  502 
Anderson,  Capt.  A.  R.  S.,  20 
Andrews,  Dr.,  156 
Animal  behaviour,  187,  628 
Animal  society,  criteria  of,  345 
Animate,  the,  624 
Antarctic    nematodes,    96 ;    shore 

fauna,  142 
Ant-hill,  326 
Ants  and  Aphides,  1 7  ;  and  plants, 

285-287  ;  and  seeds,  272  ;  har- 
vesting, 349 
Aquatic  insects,  451 
Arboreal  animals,  125 
Archer  or  spitting  fish,  14 
Arctic  tern,  165 
Argyroneta,  115 


'  Aristotle's  Lantern,'  524 
Arthus,  M.,  503 
Association,  242 
Audacity  of  Life,  148 
Avebury,  Lord,  255,  276 

Bacteria,  87,  109,  111  ;  soil,  271  ; 

luminescence  of,  490 
Baitsell,  G.  T.,  446 
Balance  of  Nature,  264 
Baldner,  469 

Baldwin,  Prof.  J.  Mark,  517 
Ballowitz,  Prof.,  30 
Barbour,  Thomas,  270 
Barnacles,  448 
Bataillon,  385 
Batesian  mimicry,  32 
Bateson,  516,  582 
Bats  and  birds,  struggle  between, 

20 

Becquerel,  483 
Beddard,  F.  E.,  532 
Beebe,  620 
Bee-hive,  339 
Bee -hunter,  425 
Bees  and  flowers,  274 
Beetles  in  ants'  nests,  52 
Behaviour,    capacity    for,    476 ; 

intelligent,  241 
Berg,  L.  S.,  113 
Bergson,  5,  208,  241,  477,  507, 

634,  641,  646 
Bernard,  Claude,  279 
Bert,  Paul,  85 
Bethe,  238 
'  Big  Trees,'  153 
Birds,  adaptations  of,  124  ;    and 

bats,  20  ;  distributing  animals, 

114 

Bird-bergs  of  Lapland,  8,  9 
Birgus,  119 


651 


652 


INDEX 


Bishop,  W.  L.,  230 

Bitterling,  273 

Blind  cuttlefish,  92 

Blood,  individuality  of,  509 

Bluffing,  231 

Bohn,  193,  208,  243 

Bombus,  nest  of,  343 

Bonnier,  Gaston,  234,  276 

Boobies  and  frigate  birds,  20 

Bordage,  E.,  563,  602 

Bordas,  L.,  151 

Boring,  Dr.,  147 

Boring  gastropod,  64 

Bottomley,  Prof.,  298 

Bourgeois,  J.,  33 

Bouvier,  234,  245 

Bread-winning,  variety  of,  12 

Brehm,  8,  9 

Brine  shrimps,  108,  136 

Brooding,  428 

Bryant,  H.  C.,  43-48 

Buchanan,  J.  Y.,  73,  84,  91 

Biichner,  201 

Buckland,  J.,  366 

Bugnion,    Prof.,    217,    218,    219, 

336,  337,  525 
Bulman,  G.  W.,  251 
Butler,  Samuel,  60 
Biitschli,  481 
Buttel-Reepen,  234,  257 
Butterflies,  odours  of,  25 

Caddis  larvae,  nets  of,  137 
Cajal,  Ramon  y,  390 
Caiman,  Dr.  W.  T.,  289 
Carnivorous  plants,  283 
Casualties,  128 
Cave  animals,  122 
Cavers,  Prof.  F.,  280 
Challenger,  82 
Cheese-fly  larv®,  151 
Chilton,  Prof.  Charles,  289 
Chromosomes,  380-381 
Chun,  92 
Cigale,  455 

Circulation  of  matter,  110 
Claparede,  499-500 
Clarke,  W.  Eagle,  164,  171 
Clark,  Dr.  A.  H.,  521 
Clark,  Dr.  H.  L.,  555 
'  Clever  Hans,'  255 
Clifford,  Prof.  W.  K.,  477,  633 


Climbing  fishes,  145 

Clods  on  birds'  feet,  114 

Cobb,  N.  A.,  96 

Cohendy,  Michel,  298 

Collett,  229 

Coloration,   protective,   29,   539; 

attractive,  550 

Colour  adaptations,29,  30,  534 
Colour-change,  in   fishes,   29 ;    in 

horned  lizards,  46  ;    in  prawns, 

72  ;   in  winter,  162 
Colour  of   deep-sea   animals,  94  ; 

of  sea,  73 

Commensalism,  292 
Continuity  of  germ-plas  .r>,  378 
Continuance  of  life,  372 
Controllability  of  life,  264 
Convergent  adaptations,  124 
Convoluta,  196,  369,  534 
Co-operation,  327 
Copepods,  104 
Coralline  zone,  56 
Cormorants,  106 
Cotte,  Jules,  312 
Coupin,  Henri,  15,  16 
Courtship  among  animals,  410 
Cowles,  R.  P.,  35,  36 
Crabs,  masking  of,  236 
Credner,  112 
Cresson,  Prof.,  434 
Grassland,  39,  40,  64 
Ctenophores,  74 
Cuckoo,  223;    habits  of,  315 
Cuckoo-spit,  40-42 
Cuenot,  120 
Cunningham,  528 


Dakin,  Prof.,  79 

Dancing  mice,  247 

Darwin,  114,  130,  202,  203,  275 

Darwin,  Francis,  252 

Dean,  Prof.  Bashford,  470 

Death,  439  ;   feigning,  230 

Deep-sea  animals,  88  ;   colour  of, 

94 

Deep-sea,  darkness  of,  86  ;  depth 
of,  83  ;  fauna  of,  81  ;  pressure, 
83  ;  temperature,  85  ;  signifi- 
cance of,  98 

Deep-sea  fishes,  eyes  of,  96; 
voracity  of,  17 


INDEX 


653 


Deep  water  of  lakes,  104 
Delage,  378,  383 
Dendy,  Prof.  A.,  589 
Dependence,  mutual,  271 
Desiccation  of  Entomostraca,  107 
Development,  374,  478 
Dewitz,  Dr.  J.,  392 
Differentia,!  sensitiveness,  193 
Dixey,  Dr.  F.  A.,  25,  26 
Dodd,  F.  P.,  426 
Dogwhelk,  65 

Domestication  by  ants,  350 
Downbreaking     and     upbuilding, 

475 

Dragon-flies  and  mosquitoes,  22 
Drama  of  life,  1-53 
Driesch,  Dr.  Hans,  209,  635,  641 
Drzewina,  Anna,  245 
Dublin,  Dr.,  356-357 
Dudley,  Prof.  W.  R.,  154-155 
Dwarf  Plankton,  109 

Earth,  the  living,  270 

Earthworms,  119,  121 

Echinoderms,  446 

Edible  birds'  nests,  530 

Edinger,  243 

Educated  animals,  254 

Eels,  229,  458  ;   migration  of,  630 

Egg-carrying  by  male  fish,  522 

Egg-case  of  skate,  527 

Egg-eating  snake,  523 

Egg-tooth,  616  ;    of  chick,  525 

Emery,  Prof.,  49 

Entelechy,  634 

Environment,  organism  and,  6,  7  ; 

the  fitness  of,  579 
Epizoic  associations,  287 
Escherich,  Prof.,  217,  220 
Evolution,  conservation  in,  621  ; 

continuity  of,  639  ;    great  steps 

in,    575 ;     main    lines    of,    5 ; 

method  of,  582 
Existence,  struggle  for,  18 
Eyelid,  the  third  in  man,  614 
Eyes,   of   cave-animals,    123 ;     of 

deep-sea  fishes,  96  ;    that  shine 

at  night,  525 

Fabre,  212,  228,  233,  418,  419,455 
Fair  Isle,  164 


Family  life  among  animals,  50 

Feigning  death,  26,  230 

Fertilization,  381  ;    internal,   121 

Fever,  531 

Fiddler  crabs,  324 

Fierasfer,  290 

Fig,   pollination,   280 

Fireflies,  417 

Fishes,  deep-sea,  95  ;  of  Lake 
Baikal,  113  ;  out  of  water,  118 

Flight,  power  of,  123 

Flowers,  bees  and,  274  ;  colour, 
278  ;  fragrance  of,  277 

Fly-trap,  Venus,  520 

Fol,  Prof.,  236 

Food  of  marine  animals,  79 

Forbes,  Edward,  56,  81 

Form,  variety  of,  11 

Fossils,  living,  620 

Fragrance,  416 

Freshwater,  colour  of,  102  ;  con- 
ditions, 101  ;  illumination  of, 
101;  temperature  of,  101 

Freshwater  animals,  103 

Freshwater  faunas,  92  ;  origin  of, 
111  ;  uniformity  of,  112 

Freshwater  insects,  451  ;  medu- 
soids,  113  ;  sponge,  108 

Frogs,  460  ;  experiments  on  eggs 
of,  385 

Functions,  every -day,  187 

Gadow,  Dr.,  11,  48 

Gain,  M.,  155 

Gaisch,  A.,  38 

Galls,  311,  399 

Gamble,  Prof.,  239,  545 

Giitke,  164,  174 

Geddes,  Prof.  P.,  6,  588 

Gemmill,  Dr.  J.  F.,  524 

Generations,  alternation  of,  444 

Germinal  selection,  517 

Giard,  Prof.,  306 

Gill,  Dr.  Theodore,  18,  25,  423 

Gilpin -Brown,  L.  G.,  328 

Gnats,  453 

Goeldi,  Prof.,  141 

Goethe,  433 

'  Golden-eight '  moth,  28 

Goodey,  T.,  271 

Gossamer,  126 

Greene,  Prof.  C.  W.,  460 


t>54 


INDEX 


Green-fly,  fertility  of,  131 

Groos,  415,  517 

Grouse,  Canadian,  Ruffed,  162 

Grouse  disease,  303 

Growing  period,  401 

Growing,  power  of,  476 

Growth,  393  ;  conditions  of,  394  ; 

in  man,  403  ;  regulation  of,  399 
Guests,  and    hosts,    51-53 ;    and 

pets  among  ants,  352 
Guide-marks,  548 
Guyer,  Prof.  M.  T.,  190 


Habitats,  strange,  139 

Habits,  change  of,  27,  156 

Habituation,  595 

Haddocks,  swarms  of,  9 

Hamon,  J.  C.,  137 

Harris,  Prof.  Fraser,  496,  530 

Harrison,  Prof.  Ross  Granville,  390 

Haunts  of  Life,  54-126 

Heather,  crowded  with  life,  7,  8 

Heligoland,  164 

Henderson,  Prof.  L.  J.,  579 

Henshaw,  H.  W.,  183-184 

Herrick,  F.  H.,  316-321 

Herubel,  Marcel,  369 

Hewitt,  Dr.  Gordon,  360 

Hibernation,  108,  161 

Hickson,  91 

Hippolyte,  545 

His,  Prof.,  392 

Hjort,  J.,  87,  92 

Hoatzin,  125,  620 

Holder,  Dr.  C.  H.,  423 

Hollande,  Dr.  A.  Ch.,  542 

Holmes,  S.  J.,  231 

Homing,  232 

Hooker,  Davenport,  192 

Hormones,  398 

Hornbills,  family  life  of,  50 

Horned  lizards,  42-48 

Horse,  a  two-toed,  611 

Horses,  thinking,  255 

Horsehair  worms,  447 

House-fly,  360,  456 

Howard,  Mrs.  A.  B.,  491 

Howard,  Dr.  L.  0.,  359 

Hoyle,  W.  E.,  491 

Hudson,  W.  H.,  250-251.  350 

Hull,  A.  F.  Basset,  149 


Hunger  and  Love,  5 
Hussakoff,  Dr.  L.,  466 
Huxley,  131,  372,  639-640 
Huxley,  Julian  S.,  557 

Implosion,  91 
Impulses,  primary,  5 
Individuality,  chemical,  507 
'  Infantile      mortality '     on      the 

sea-shore,  64 

Inference,   conceptual   and     per- 
ceptual, 242 
Insects,  wings  of,  125 
Instinct  and  intelligence,  249 
Instinct,  animal,  199  ;  limitations 

of,  227  ;  origin  of,  205 
Instinctive    behaviour,    instances 

of,  208 

Insurgence  of  life,  127,  129 
Intelligent  behaviour,  241 
Inter-relations,  intricacies  of,  263  ; 
among  freshwater  animals,  106 
Isolation,  114 
Izuka,  Akira,  133 

Jacobson,  16 
Jameson,  H.  Lyster,  313 
Japhen,  Dr.  A.,  618 
Jellyfish,  445 
Jenkinson,  Dr.,  402 
Jennings,  Prof.,  477 
Joly,  Prof.,  472 
Jordan,  K.,  53 

Kammerer,  563,  604 
Keeble,  Prof.,  239,  545 
Keibel,  Prof.  F.,  526 
Kellogg,  Prof.  V.  L.,  153 
Kelpfish,  423 
Kent,  Saville,  43 
King,  Miss  H.  D.,  564 
Krall,  256 

Lacustrine  regions,  102 
Lake  Baikal,  100,  113 
Lakes,  fauna  of,  103 
Laminarian  Zone,  56 
Land  crab,  11 9,  156 
Land  snail,  African,  132 
Lang,  Prof.  Arnold,  161 
Langerheim,  135 


INDEX 


655 


Lankester,  Sir  Ray,  136,  241,  358, 
441 

Larvae  of  flies,  136 

Latent  life,  483 

Latter,  Oswald  H.,  410 

Leduc,  Prof.  Stephan,  481 

Legendre,  499 

Lemmings,  229 

Lentz,  225 

'  Lerot,'  532 

Lessona's  law,  560 

Lichens,  297 

Liesegang's  rings,  643 

Life,  continuance  of,  372 ;  the 
cycle  of,  371  ;  curve  of,  371  ; 
drama  of,  1-53 ;  insignia  of, 
474;  insurgence  of ,  127;  powers 
of,  487  ;  subtlety  of,  501  ; 
toughness  of,  128 

Light-limit  in  sea,  86 

Limit  of  growth,  401 

Lindsay,  Miss  B.,  145 

Linkages,  267 

Littoral  zone,  56 

Liver-fluke,  307 

Lizards,  horned,  42-48 

Local  life,  488 

Loeb,  J.,  191,  194-195,  208,  383 

Lohmann,  109 

Longevity,  436 

Lotze,  3 

Love,  hunger  and,  5 

Loves  of  animals,  48 

Luciola,  the  Italian  fire-fly,  49 

Lull,  R.  S.,  124 

Luminescence,  94,  487 

Lumpsucker,  70 

MacBride,  Prof.  E.  W.,  389 
McDougall,  Dr.,  224 
Macfadyen,  Dr.  A.,  472 
Mclntosh,  Prof.  W.  C.,  39,  67 
Malaria,  269 
Mantis,  34,  418 
Marquet,  M.,  206 
Marshall,  G.  A.  K.,  32 
Masking,  35,  235;    in  crabs,  72 
Mason  bee,  227 
Matthew,  W.  D.,  578 
Maturation,  380 

Maximum  productivity,  summer 
and  autumn,  10 


Mayer,  A.  G.,  74, 228, 268 

Mayflies,  2,  452 

Mechanisms,  organisms  and,  472 

Mercier,  L.,  361 

Mermis,  447 

Metabolism,  475  ;  animal,  187 

Metchnikoff,  Prof.,  437 

Meyer,  243 

Miall,  Prof.,  137 

Migration,  162-184  ;  concrete  pro- 
blems of,  171  ;  deeper  pro- 
blems of,  174 ;  fundamental 
facts  of,  165 

Miller,  Newton,  131 

Mimicry,  32 

Minkiewiez,  236,  237,  238,  239 

Mitchell,  Dr.  P.  Chalmers,  405, 
409,  432,  547 

Mnemic  theories,  601 

Modifiability,  511 

Modifications,  individual,  592 

Mole,  518 

Moles'  nests,  fauna  of,  140 

Monaco,  Prince  of,  84 

Mongoose  in  Jamaica,  270 

Montgomery,  211 

Moore,  Prof.  B.,  80 

Morgan,  Prof.  Lloyd,  206-208, 
224,517 

Morgan,  Prof.  T.  H.,  567 

Mortensen,  Th.,  133,  171 

Mosquitoes,  and  ants,  16 ;  and 
dragon -flies,  22 

Mouthless  carp,  150 

Movements,  periodic,  175 

Muir,  Dr.  T.,  367 

Miillerian  mimicry,  33 

Muller,  Fritz,  252 

Miiller,  Hermann,  251 

Multiplication  of  freshwater 
animals,  104 

Murray,  James,  135, 143 

Murray,  Sir  John,  82,  86,  92 

Mussels  and  minnows,  273 

Nannoplankton,  80,  110 
Nature,  tactics  of,  586 
Neger,  Prof.,  282 
Nekton,  75 
Nematodes,  96 
Nerve-development,  390 
Newton,  Alfred,  166,  170,  266 


656 


INDEX 


'  Nidicolous  '   Coleoptera,   140 

'  Niners,'  464 

Noctiluca,  130 

Nototrema,  121 

Nutrition,  394 

Nutritive  chains,  62,  110 

Ogneff,  593 

Opisthocomus,  125 

Organism  and  environment,  6,  7 

Organisms  and  mechanisms,  472 

Origin  of  deep-sea  fauna,  97 

Orton,  425 

Osborn,  H.  F.,  517 

Oscillatoria,  111 

Osmotic  growths,  482 

Oxner,  243-244 

Ox-warbles,  310 

Oyster,  fertility  of,  132 

•  Painted  fish,'  293 

Palolo-worm,  71  ;  swarming  of, 
133 

Parasitism,  300 

Parental  care,  419 

Parental  instincts,  chain  of,  430- 
432 

Parthenogenesis,  artificial,  383 

'  Partial '  migrants,  167 

Past,  the  living,  606 

Paternal  care,  69,  422 

Pathology,  the  optimism  of,  589 

Pavlov,  242 

Pearls,  312 

Pearse,  A.  S.,  148,  158,  324-325 

Peckham,  Mr.  and  Mrs.,  234,  235 

Pelagic  algse,  73  ;  fauna,  73 ; 
insects,  76 ;  larvae,  66 

Penelope  spider,  141 

Peri-embryonic  fluid,  528 

Periodicities,  401 

Periophthalmus,  118 

Peters,  Dr.  Karl,  417 

Phosphorescence,  86 

Photosynthesis,  394 

Physical  conditions  of  shore  area, 
57 

Pieron,  330 

Pigeon,  passenger,  366 

Pigment  in  animals,  535 ;  sig- 
nificance of,  536 

Pineal  body,  609 


Pitcher  plant,  inter-relations  of, 

283 

Plankton,  75 
Plants     and     animals,     relations 

between,  281 

Plasticity  of  life,  156,  511 
Play  of  animals,  408 
Plover,  Pacific  Golden,  183,  184 
Pocock,  R.  I.,  34,  37 
Polar  body,  381 

Poulton,  Prof.  E.  B.,  33,  34,  539 
Primal  impulses,  5 
Productivity,   129 ;    in  the  open 

sea,  10 

Protective  coloration  of  crab,  72 
Protozoa,  immortality  of,  440 
Przibram,  Prof.  H.,  569 
Putter,  Prof.,  79 
Pycraft,  W.  P.,  412,  463,  549 
Python,  meals  of,  17 

Race,  the  individual  and  the,  432 

Racovitza,  123,  146 

Rat,  fertility  of,  131 

Reaction,  changes  of,  194-195 

Read,  Prof.  Carveth,  249 

Red  snow,  135 

'  Reducing  division,'  380 

Reflex  actions,  188 

Regeneration,  571 

Regeneration  and  embryonic 
development,  569 

Regeneration,  imperfect,  567 

Regeneration  of  lost  parts,  in- 
stances of,  543,  552 

Regenerative  capacity,  unequal 
distribution  of,  558 

Registering  experience,  591 

Relict  seas,  112 

Reproducing,  power  of,  478 

Resemblance  to  surroundings,  28 

Response,  effectiveness  of,  510 

Revivification  of  water-fleas,  107 

Rhinoderma,  121 

Rhythmic  movements,  196 

Richet,  503 

Ritter,  W.  E.,  139 

Ritzema-Bos,  Dr.,  519 

Robinson,  Louis,  226 

Rock-borers,  145 

Romanes,  241,  253,  255 

Ross,  Sir  John,  81 


INDEX 


657 


Rothney,  214 
Rotifers,  104 
Rousselet,  C.  F.,  23 
Roux, 473-475 
Rubbell,  A.,  314 

Russell,  Dr  ,and  Hutchinson,  Dr., 
270 

Sable  Island,  115 

Sacculina,  309 

Sack,  Albert  von,  543 

Salamander,  colour  change  in, 
38  ;  in  trees,  139 

'  Sally,'  255 

Salmon,  459 

Salt,  amphibians  and,  148 

Sanderson,  Sir  J.  B.,  510 

Scales,  amphibian,  616, 

Sea-cucumber's  defence,  24 

Sea-horse,  69,  422 

Sea-lamprey,  465 

Sea-lions,  415 

Sea-otter  on  kelp  beds,  140 

Seasonal  changes  in  freshwaters, 
104 

Seasons,  Biology  of  the,  159 

Sea-spider,  69 

Sea-urchin  eggs,  experiments  with, 
378,  383  ;  weapons  of,  62 

Seeds,  ants  and,  272 

Self-advertisement,  36 

Semon,  Prof.,  160,  603 

Senescence,  443 

Senility,  443 

Sequoia,  153 

Shackleton,  96 

Shaler,  Prof.,  579 

Shells  of  Molluscs,  63 

Shelter  associations,  290 

Shipley,  Dr.  A.  E.,  7,  8,  303 

Shore  area,  55  ;  physical  condi- 
tions of,  57  ;  struggle  in,  61 

Shore  crab,     451 

Shore,  evolutionary  significance 
of,  72  ;  fauna,  55 

Shrews,  dentition  of,  613 

Signalling   among    Termites,    336 

Signals  between  sexes,  417 

Simulacra  vitae,  481 

Simulium  larva,  136 

Skua  and  herring-gull,  16 

Slave-making  among  ants,  354 


Sleep,  494 

Slipper  animalcule,  133-134 

Slipper-limpet,  425 

Sloth's  hair,  alga  on,  281 

'  Snowshoes'  of  grouse,  521 

Social  bees,  evolution  of,  341 

Societies,  animal,  323 

Sollas,  1 12 

Soule,  Caroline  G.,  228 

Southwell,  T.,  526 

Spalding,  225 

Sparrows  in  United  States,  270 

Species,  number  of,  10 

Spelajoniscus,  123 

Spencer,  Herbert,  97,  400 

Sphex-wasp,  20y,  213 

Spider  crabs,  masking  of,  236 

Spiders,  ballooning,  126 

Spider's  web,  210 

Sponge,  freshwater,  443 

Stager,  Dr.  R.,  139 

Starfish,  fecundity  of,  133 

Starfish  with  young,  68 

Starling,  Prof.  E.  H.,  627 

Stickleback's  nest,  69 

Stockard,  Dr.  C.  R.,  613 

Stone,  fauna  of  a,  134 

Structural  coloration,  536 

Struggle  among  ova,  66 

Struggle    for   existence,    18,    66 ; 

Darwinian  view  of,  19-20  ;    in 

shore  area,  61 
Subterranean  animals,  122 
Sumner,  F.  B.,  470 
Surinam  toad,  121,  424 
Surroundings,  resemblance  to,  28, 

31 

Swooping  animals,  124 
Symbiosis,  295 

Tactile  organs,  92 
Tanganyika,  113 
Temperature  and  growth,  396 
Temperature,  influence  of,  95 
Tenacity  of  life,  151 
Termites,  333  ;   black,  215 
Tern,  nest  of  White,  149 
Terrestrial    animals,    adaptations 

of,  120  ;   origin  of,  119  ;    under 

water,  146 

Terrestrial  fauna,  117 
Thienemann,  Dr.,  165 

u  u 


658 


INDEX 


Thompson,  Prof.  D'Arcy,  416 

Thomson,  Dr.  Stuart,  552 

Thomson,  Sir  Wyville,  81,  91 

Thorndike,  Prof.,  245-246 

Thrust  and  parry,  23 

Tidman's  sea-salt,  108,  136 

Tile  fish,  156 

Time,  trading  with,  591 

Tissue  regeneration,  555 

Tornier,  G.,  152 

Transparent  animals,  78 

Tree-frogs,  tadpoles  of,  149 

Trial  and  error,  245 

Triton,  lens  of,  570 

Tropisms,  191  ;   establishment  of, 

197 

Tubularia,  66 
Tunicates,  45-47 
Turner,  232 
Typhobia,  113 

Variability,  479 

Venus'  Flower  Basket,  91 

Venus  girdle,  78 

Vest  gial  structures,  607 

Vinson,  15 

Viscachas,  350 

Vitalism,  622 

Vogt,  135 

Vries,  de,  516,  582 

Vultures  13,  14 

Wagner,  115 

Wallace,  A.  R.,  179,  414,  547-549 
Wallich,  81 
Walther,  J.,  97 
Warm-bloodedness,  530 
Warning  coloration,  547 
Wasmann,  52 
Wasp,  nest  of,  344 


Wasp,  solitary,  224 

Water -fleas,  107 

Water-spider,  115 

Watson,  William,  99 

Waves    of    Life,   successive,    141 

Way-finding  of  birds,  180 

Ways  of  Life,  186 

Weapons,  24 

Weber,  Prof.  Max,  493 

Web  of  Life,  Man  and,  357 

Web  of  Life,  243 

Darwinian   conception  of,  40 
Weismann,  205,438,480,517,562, 

568 

Wery,  J.,  279 
Wesenberg-Lund  C.,  137 
Wetting  of  water  animals,  115 
Whales'  hair,  617 
Whelk,  65 

Whitney,  Dr.  D.  D.,  612 
Willey,  Prof.,  289 
Wilson,  Prof.  E.  B.,  378 
Wilson,  Prof.  H.  V.,  485 
Wings,  125 
Winter  conditions   in   freshwater, 

108 

Winter  eggs,  108 
Wintrebert,  28 

Woodruffe,  Prof.  L.  L.,  133,  142 
Worcester,  Dean  C.,  20 

Yellow-fever,  365 
Yerkes,  247 
Young  animals,  405 
Youth,  the  purpose  of,  408 
Yung,  Prof.  E.,  233 

Ziegler,  H.  E.,  262 
Zoophytes,  444 
Zulueta,  A.  de,  305 


Butler  &  Tanner  Frame  and  London 


A     000029433     o 


